#!/bin/cat
$Id: FAQ.Gmail.txt,v 1.112 2025/08/30 02:18:17 gilles Exp gilles $

This document is also available online at
https://imapsync.lamiral.info/FAQ.d/
https://imapsync.lamiral.info/FAQ.d/FAQ.Gmail.txt

=======================================================================
              Imapsync tips for Gmail accounts.
=======================================================================

Questions answered in this FAQ are:


Q. Can I use imapsync to transfer from or to Gmail accounts?

Q. Even after several syncs the number of messages differs
   largely between imapsync and the Gmail web interface.
   What can I do?

Q. How many days does it take to transfer X GB?

Q. What is the Gmail free maximum storage size? 
A. 15 GB in 2025. Need more?
   https://gsuite.google.com/pricing.html

Q. How to synchronize from Gmail to Gmail?

Q. How to synchronize from XXX to Gmail?

Q. How to synchronize from Gmail to XXX?

Q. I can't authenticate with Gmail via IMAP
   and Gmail says 
   "Please log in via your web browser"
   or it says 
   "Application-specific password required: https://support.google.com/accounts/answer/185833 (Failure)"

Q. Can not open imap connection on [imap.gmail.com]
   Unable to connect to imap.gmail.com

Q. I want to sync the Sent folder only, what is it on Gmail?

Q. From Gmail to Gmail, I want to keep Categories. What can I do?

Q. The context is a Gmail account at the source, but not Gmail at the
destination. I want cross-duplicates, different Gmail folders/labels
generating duplicate messages across folders on the destination,
except for the "All Mail" folder.

Q. I can't sync more than 1000 messages in each Gmail folder.
   What can I do?

Q. What are the Gmail imap names of the folders 
   "Sent" "Trash" "Drafts" "Junk" "Flagged" and "All"?

Q. Can I transfer Gmail "Chat" messages with imapsync?

Q. Can I safely use --useuid or --usecache for Gmail transfers?

Q. Can I use --syncduplicates Gmail transfers?

Q. Gmail does not really delete messages in folder [Gmail]/All Mail
   What happens? What can I do?

Q. Can I use the Extension of the SEARCH command: X-GM-RAW described at
   https://support.google.com/mail/answer/7190?hl=en
   https://developers.google.com/gmail/imap_extensions#extension_of_the_search_command_x-gm-raw

Q. How to avoid the [IMAP] prefix on Gmail side?

Q. Does imapsync have the capability to do 2 stage authentication?

Q. How to use XOAUTH2 to globally authenticate gmail users?

Q. How to use XOAUTH to globally authenticate gmail users?

Q. How to use a Gmail account to backup several different imap accounts?

Q. How to migrate email from gmail to google apps?


Now the questions again with their answers.

=======================================================================
Q. Can I use imapsync to transfer from or to Gmail accounts?

A. Yes. The IMAP access to a Gmail account is not always allowed 
by default so here is how to allow IMAP for a Gmail account:
 -> Do not go to "Manage your Google Account" (the upper right icon with your Google face)
 -> Instead, go to Gmail at https://mail.google.com/
 -> Click on Settings, the gear button on the upper right of Gmail.
 -> Click on "See all settings" at the top of the pull down menu.
 -> Go to the tab "Forwarding and POP/IMAP"
 -> Go down to "IMAP Access"
 -> Activate the radio button "Enable IMAP"
 -> Click on the button "Save changes" at the bottom of the page.

That's not finished, there is also the authentication issue to consider.
There are three different ways to authenticate to Gmail with Imapsync,
either:

1) "App password with 2-step verification", which is currently the
only way to authenticate on Gmail with the imapsync online service
https://imapsync.lamiral.info/X/
An app password is only available for an individual account.

2) OAUTH2 for individual Gmail authentication, see
https://imapsync.lamiral.info/oauth2/oauth2_imap/README_oauth2.txt

3) for Gmail groups, on any OS, see
https://imapsync.lamiral.info/FAQ.d/FAQ.XOAUTH2.txt


Back to 
1) So, how to setup an "app password" on Gmail?

Short answer: first, you have to activate "2-step verification".
Then, once activated, "2-step verification" will allow you to generate
an "App password" at https://myaccount.google.com/apppasswords

Now, the details.
Go to
https://myaccount.google.com/security
and sign in with the account you want to transfer email to or from.
Go to the "Signing in to Google" part of the security page and follow
the process to activate the "2-step verification", until it is ok.

Then, in the part "How you sign in to Google" click on the "2-step
verification" line. There, at the bottom of the page, you will be
proposed to generate an "App passwords".

As an alternative, you can also go to 
https://myaccount.google.com/apppasswords
it will bring you at the same place.

Then, follow the instructions to get a 16 characters password. On the
pull-down button "Select app", choose "Other (Custom name)" and call
it imapsync for example. The name doesn't matter.  Now, use this
password to access the mailbox with imapsync. If you copy/paste the
password, remove the blanks inside the password, the blanks are not
part of the password, they're just there to facilitate the reading but
they're bad to authenticate with imapsync. If you leave the blanks,
you may encounter an authentication error.

The following document details what I've just described and other
useful tips about app passwords:
https://support.google.com/accounts/answer/185833?hl=en 

Even if Google says "Every App Password is only used once", it's false
and the same password can be used many times.

Here is another document about Gmail app passwords, more graphical:
https://www.limilabs.com/blog/using-app-passwords-with-gmail

Other questions related to Gmail and imapsync at
https://imapsync.lamiral.info/FAQ.d/FAQ.Gmail.txt

=======================================================================
Q. Even after several syncs the number of messages differs
   largely between imapsync and the Gmail web interface.
   What can I do?

A. Turned off "Conversation views" on Gmail.
With "Conversation views" turned off, Gmail shows the exact message 
count for each folder and it matches what imapsync shows. 
With "Conversation views" on, a single conversation can have 
multiple messages and it doesn't match what imapsync presents.
(Thanks to Karthik.V for this input)

=======================================================================
Q. How many days does it take to transfer X GB?

A. Gmail has usage limits per day and can use throttles when
   they are overtaken
   https://support.google.com/a/answer/1071518?hl=en
   From the previous link:

   * Upload with IMAP: 500 MB per day.
   It should be 2X days to upload  X GB to Gmail.
   That's not much, isn't it?
   
   Imapsync throttle options should be 
   --maxbytespersecond 5787 --maxbytesafter 500_000_000
   
   but instead, I suggest to use 
   --maxbytespersecond 300_000 --maxbytesafter 3_000_000_000
   for uploading messages to Gmail because those higher values
   work well. Option --gmail2 implies those values.
   
   * Download with IMAP: 2500 MB per day.
   It's X/2.5 days to download X GB from Gmail.
   
   Imapsync throttle options should be
   --maxbytespersecond 28_935 --maxbytesafter 2_500_000_000
   
   but instead, I suggest to use
   --maxbytespersecond 300_000 --maxbytesafter 3_000_000_000
   for downloading messages from Gmail because those higher values
   work well. Option --gmail1 implies those values.
  
   They are empirical values that work in practice.
   Try upper values and see if they still work. 
   I would be grateful when you report them to me.

   How Gmail says limits are reached?
   This is either a disconnection with
   "BYE Session expired, please login again"
   or a very small rate, less than 1 Kib/s

https://imapsync.lamiral.info/FAQ.d/FAQ.Gmail.txt
=======================================================================
Q. How to synchronize from Gmail to Gmail?

A. Use the following example:

imapsync --user1 account1@gmail.com \
         --password1 gmailsecret1 \
         --user2 account2@gmail.com \
         --password2 gmailsecret2 \
         --gmail1 --gmail2 

Or, replacing what does --gmail1 --gmail2 (values are from imapsync 2.290):

imapsync --host1 imap.gmail.com \
         --ssl1 \
         --user1 account1@gmail.com \
         --password1 gmailsecret1 \
         --host2 imap.gmail.com \
         --ssl2 \
         --user2 account2@gmail.com \
         --password2 gmailsecret2 \          --maxbytespersecond 300_000  \
         --maxbytesafter 3_000_000_000 \
         --automap \
         --maxsleep 2 \
         --useheader X-Gmail-Received \
         --useheader Message-Id \
         --synclabels \
         --resynclabels \
         --idatefromheader \
         --exclude "\[Gmail\]$" \
         --folderlast  "[Gmail]/Sent Mail" \
         --folderlast  "[Gmail]/Important" \
         --folderlast  "[Gmail]/Starred" \
         --folderlast  "[Gmail]/Drafts" \
         --folderlast  "[Gmail]/Trash" \
         --folderlast  "[Gmail]/Spam" \
         --folderlast  "[Gmail]/Chats" \
         --folderlast  "[Gmail]/All Mail"

With --gmail1 --gmail2 you can override the parameters
that are activated by them, for example:

imapsync ... --gmail1 --gmail2 --maxbytespersecond 50_000 --noautomap

Explanations:


--maxbytespersecond 300_000  ( 300 kBytes/s ) option is here to avoid 
locking or errors when imap transfers exceed Gmail maximum limit. 
See http://support.google.com/a/bin/answer.py?hl=en&answer=1071518
--maxbytespersecond 300_000  is not mandatory in the sense Gmail may 
allow you to use an upper value than 1 GBytes per 24h without 
disconnections. If you count well, it should be 10_000, not 300_000 .

--maxbytesafter 3_000_000_000 option is there because 
option --maxbytespersecond 300_000  is unnecessarily slow if the Gmail 
account size is less than 3 GB.

--maxsleep 2 is to avoid sleeping more than 2 seconds when 
the --maxbytespersecond value implies a long sleep between 2 copies.

--idatefromheader sets the internal dates on host2 to the same as the
ones in "Date:" headers. It is because Gmail displays the listing of 
messages ordered by their internal dates, which can be a mess sometimes.
Sorting by the "Date:" headers gives a better presentation.

--automap is not mandatory but it's a feature to automatically
map folder names based on the Gmail user configuration itself, par account.
It will save manual folder names changes or the use of --regextrans2 
or --f1f2 to map folder names.
For example, imap folder "[Gmail]/Sent Mail" may be mapped as one of
E-mails enviados
Enviada
Enviado
Gesendet
Gönderildi
Inviati
Sendt
Skickat
Verzonden
etc.
on both sides, host1 or host2, maybe differently, sometimes in 
incomprehensible alphabets, a headache for imap sysadmins.
See a listing here:
http://stackoverflow.com/questions/2185391/localized-gmail-imap-folders/2185548#2185548

--exclude "\[Gmail\]$"   is just there to avoid a warning error
when selecting this not used folder.

Be aware that --gmail1 --gmail2 is a special case, it's not what
--gmail1 does plus what --gmail2 does when they are not invoked 
together.


https://imapsync.lamiral.info/FAQ.d/FAQ.Gmail.txt
=======================================================================
Q. How to synchronize from XXX to Gmail?

A. Use the following example:

imapsync --host1 mail.oldhost.com     \
         --user1 my_email@oldhost.com \
         --password1 passwordold   \
         --user2 my_email@gmail.com \
         --password2 gmailsecret \
         --gmail2

Or, replacing what does --gmail2 (values are from imapsync 2.290):
(For Linux only because of the quotes)

imapsync --host1 mail.oldhost.com     \
         --user1 my_email@oldhost.com \
         --password1 passwordold   \
         --host2 imap.gmail.com \
         --ssl2 \
         --user2 my_email@gmail.com \
         --password2 gmailsecret \
         --maxbytespersecond 300_000 \
         --maxbytesafter 3_000_000_000 \
         --automap    \
         --expunge1   \
         --addheader  \
         --maxsleep 2 \
         --idatefromheader \
         --exclude "\[Gmail\]$"  \
         --regextrans2 's,\[Gmail\].,,' \
         --regextrans2 's,^ +| +$,,g'   \
         --regextrans2 's,/ +| +/,/,g'  \
         --regextrans2 's/['"'"'\\^"]/_/g' \
         --folderlast  "[Gmail]/Sent Mail" \
         --folderlast  "[Gmail]/Important" \
         --folderlast  "[Gmail]/Starred" \
         --folderlast  "[Gmail]/Drafts" \
         --folderlast  "[Gmail]/Trash" \
         --folderlast  "[Gmail]/Spam" \
         --folderlast  "[Gmail]/Chats" \
         --folderlast  "[Gmail]/All Mail"


Starting from imapsync 1.926 a --regextrans2 replacing 
all blanks, was:

        --regextrans2 "s/[ ]+/_/g" 

With --gmail2 you can override the parameters
that are activated by them, for example:

imapsync ... --gmail2 --maxbytespersecond 50_000 --noautomap --maxsleep 0

Explanations:

--maxbytespersecond 300_000 ( 300 kBytes/s ) option is here to avoid 
locking or errors when imap transfers exceed Gmail maximum limit. 
See http://support.google.com/a/bin/answer.py?hl=en&answer=1071518
--maxbytespersecond 300_000 is not mandatory in the sense Gmail may 
allow you to use an upper value than 1 GBytes per 24h without 
disconnections. If you count well, it should be 10_000, not 300_000.

--maxbytesafter 3_000_000_000 option is there because 
option --maxbytespersecond 300_000 is unnecessarily slow if the Gmail 
account size is less than 3 GB. Counting well, it should 
be 500_000_000, not 3_000_000_000, but 3 GB is usually ok.

--maxsleep 2 is to avoid sleeping more than 2 seconds when 
the --maxbytespersecond value implies a long sleep between 2 copies.

--maxsleep 0 cancels any imapsync bandwidth restriction given by
the options --maxbytespersecond or --maxmessagespersecond
It does not cancel the imap server bandwidth restrictions.

--idatefromheader sets the internal dates on host2 to the same as the
ones in "Date:" headers. It is because Gmail displays the listing of 
messages ordered by their internal dates, which can be a mess sometimes.
Sorting by the "Date:" headers gives a better presentation.

--automap is optional but it will save manual folders names
changes or the use of --regextrans2 or --f1f2 to map folder names.

--expunge1 is optional. It deletes messages marked \Deleted on host1.
Imapsync syncs messages with all their flags, Gmail takes the messages
marked \Deleted but deletes or moves them just after.
Option --expunge1 really removes messages marked \Deleted on host1 
so they are not synced at all.


The --addheader option is there because "Sent" folder messages 
sometimes lack the "Message-Id:" and "Received:" headers needed 
by imapsync to identify messages (only when --useuid is not used). 
So option --addheader adds a "Message-Id" header consisting of
the imap UID of the message on the host1 folder, like
"Message-Id: 12345@imapsync".

--exclude "\[Gmail\]$" is there to avoid a small examine/select error:
"Could not examine: 43 NO [NONEXISTENT] Unknown Mailbox: [Gmail] 
(now in authenticated state) (Failure)".

--regextrans2 "s/[ ]+/_/g" is there to convert blank characters not 
accepted by gmail to character _ underscore. In fact only leading
and trailing blank characters are problems with gmail, and
also successive blanks ending with the IMAP error 
"NO [CANNOT] Folder contains excess whitespace (Failure)"
If you want to change only leading and trailing blank characters
then use the following instead
On Linux/Unix:
  --regextrans2 "s,(/|^) +,\$1,g" --regextrans2 "s, +(/|$),\$1,g"
On Windows:
  --regextrans2 "s,(/|^) +,$1,g" --regextrans2 "s, +(/|$),$1,g"


--regextrans2 "s/[\^]/_/g" is mandatory.  It converts, since
not accepted by gmail, character ^ to character _ underscore.

--regextrans2 's/['"'"'\\^"]/_/g' is optional. It converts 
characters ' or " or \ to character _ underscore.

You can select folders exported to imap within the gmail preferences.
Select or unselect some "System labels", depending on your needs.


https://imapsync.lamiral.info/FAQ.d/FAQ.Gmail.txt
=======================================================================
Q. How to synchronize from Gmail to XXX?

A. Use this example:

imapsync \
           --user1     foo@gmail.com \
           --password1 gmailsecret \
           --host2     imap.example.org \
           --user2     tata \
           --password2 tatasecret \
           --gmail1

Or, replacing what does --gmail1 (values are from imapsync 2.290):

imapsync \
           --host1     imap.gmail.com \
           --ssl1 \
           --user1     foo@gmail.com \
           --password1 gmailsecret \
           --host2     imap.example.org \
           --user2     tata \
           --password2 tatasecret \
           --maxbytespersecond 300_000 \
           --maxbytesafter 3_000_000_000 \
           --automap \
           --maxsleep 2 \
           --skipcrossduplicates \
           --useheader="X-Gmail-Received" \
           --useheader "Message-Id" \
           --regextrans2 "s,\[Gmail\].,," \
           --folderlast  "[Gmail]/All Mail"

With --gmail1 you can override the parameters
that are activated by them, for example:

imapsync ... --gmail1 --maxbytespersecond 500_000 --noskipcrossduplicates --noautomap

Explanations:

--maxbytespersecond 300_000 ( 300 kBytes/s ) option is here to avoid 
locking or errors when imap transfers exceed Gmail maximum limit. 
See http://support.google.com/a/bin/answer.py?hl=en&answer=1071518
--maxbytespersecond 300_000 is not mandatory in the sense Gmail may
allow you to use an upper value without disconnections.

--useheader="X-Gmail-Received" --useheader "Message-Id" are not
mandatory. I use them because I found (several years ago, it may have
changed) that Gmail always adds a different header "X-Gmail-Received:"
to all messages it gets. So the identification by imapsync can not
fail using this header. "Message-Id" is there for safety about this
Gmail rule.

--automap is optional but it will save manual folder names changes or
the use of --regextrans2 to map folder names.

--regextrans2 "s,\[Gmail\].,,"
If your destination imap server doesn't like the "[Gmail]" name, 
get rid of this "[Gmail]" part with that.

You can select folders exported to imap within the Gmail preferences,
for example, you may unselect all "System labels".

--skipcrossduplicates is optional but it can save Gigabytes of hard
disk memory. Within imap protocol, Gmail presents Gmail labels as
folders, so a message labelled "Work" "ProjectX" "Urgent" ends up in
three different imap folders "Work" "ProjectX" and "Urgent" after an
imap sync. Option --skipcrossduplicates prevent this behavior.

An issue with --skipcrossduplicates is that the first label synced by
imapsync goes to its corresponding folder but other labels are then
ignored. You can choose what labels have priority by using the
--folderfirst option. For example, --folderfirst "Work" will sync
messages labelled "Work" before messages labelled "CanWait" or
"Urgent". By default imapsync syncs folders (Gmail labels) using the
classical alphanumeric order.

Option --folderlast "CanWait" will sync to the folder CanWait the
messages that only have the label CanWait, doing it at the end of 
the sync.


Option --folderlast "[Gmail]/All Mail", in conjunction with option
--skipcrossduplicates will only put in "[Gmail]/All Mail" the messages
that are not labelled at all.


https://imapsync.lamiral.info/FAQ.d/FAQ.Gmail.txt
=======================================================================
Q. I can't authenticate with Gmail via IMAP
   and Gmail says 
   "Please log in via your web browser"
   or it says 
   "Application-specific password required: https://support.google.com/accounts/answer/185833 (Failure)"

A0. My current settings on two Gmail accounts are made
with three steps 0) 1) 2)

0) Login via a web browser to the Gmail account concerned.

1) The 2-step verification is ON
https://myaccount.google.com/security?hl=en&pli=1&nlr=1#signin

2) Access for less secure apps is turned ON
https://www.google.com/settings/security/lesssecureapps
https://support.google.com/accounts/answer/6010255?hl=en

A1. See Coert Grobbelaar solution:
https://web.archive.org/web/20150906230041/http://security.stackexchange.com/questions/86404/how-do-i-interact-with-google-to-import-email-via-imapsync
https://support.google.com/accounts/answer/185833

A2. I had the same issue one time (mars 2015) logging to Gmail 
with imapsync.
The Gmail imap message error said "Please log in via your web browser"
so I logged for this account via a web browser. Then,
it asked me to receive a code via a mobile, I said yes,
I entered the code and everything went ok on next syncs
with imapsync. 

A1 again. Since people rarely follow links in a txt file, I reproduce
Google documentation from the link
https://support.google.com/accounts/answer/185833

Sign in using App Passwords
An App Password is a 16-digit passcode that gives a non-Google app or 
device permission to access your Google Account. 
App Passwords can only be used with accounts that 
have 2-Step Verification turned on.

When to use App Passwords
To help keep your account secure, use "Sign in with Google" to 
connect apps to your Google Account. 
If the app you’re using doesn’t offer this option, you can either:

Use App Passwords to connect to your Google Account
Switch to a more secure app
Create & use App Passwords
Note: If you use 2-Step-Verification 
( https://support.google.com/accounts/answer/185839 )
and are seeing a "password incorrect" error when trying to access 
your Google Account, an App Password may solve the problem.

* Go to your Google Account https://myaccount.google.com/
* On the left navigation panel, choose Security.
* On the "Signing in to Google" panel, choose App Passwords. 
  If you don’t see this option:
  * 2-Step Verification is not set up for your account.
  * 2-Step Verification is set up for security keys only.
  * Your account is through work, school, or other organization.
  * You’ve turned on Advanced Protection for your account.
* At the bottom, choose Select app and choose the app you’re using.
* Choose Select device and choose the device you’re using.
* Choose Generate.
* Follow the instructions to enter the App Password. 
  The App Password is the 16-character code in the yellow bar on your device.
* Choose Done.

Most of the time, you’ll only have to enter an App Password once per 
app or device, so don’t worry about memorizing it.

=======================================================================
Q. Can not open imap connection on [imap.gmail.com]: 
   Unable to connect to imap.gmail.com

A0. It looks like this issue is related to ipv6. Both ipv4 and ipv6 
protocols should work with gmail and imapsync, I test that regularly, 
imapsync works fine for both ipv4 and ipv6. 
If you disable ipv6 then disable also ipv6 resolution! 

The default names resolution order is to present ipv6 name resolutions 
first. If you know how to make ipv4 answers be taken before ipv6 
then tell me.

A1. First solution, run imapsync with the option --inet4:

   imapsync ... --inet4

A2. A second solution is to use directly gmail ipv4 ip address:

  imapsync ... --host1 64.233.184.108 

In case it changes, get it with any command showing the imap.gmail.com 
name resolution, try one of those:

  nslookup imap.gmail.com
  host     imap.gmail.com
  ping     imap.gmail.com

Or go to http://ping.eu/nslookup/ to get the resolution.

Thanks to Chris Nolan to report, understand and fix this issue!



=======================================================================
Q. I want to sync the Sent folder only, what is it on Gmail?

A1. Use:

  imapsync ... --folder "[Gmail]/Sent Mail"

A2. In fact, by configuration from the user, it can be another folder 
    name presented in IMAP. Use --automap --dry to see this mapping.
    See below 

=======================================================================
Q. From Gmail to Gmail, I want to keep Categories. What can I do?

A. First, read a document to learn how to play with Gmail Categories:
https://support.google.com/mail/answer/3094499

Categories are not presented in IMAP in Gmail, so synchronizing them 
with imapsync requires some work.

Let's say I want to synchronize the category named "Updates".

1. Create a label "Updates_L", or name it as you want. You can't 
   create a label named "Updates" like the category name because
   Gmail will refuse to create it, saying it's a reserved name.

2. Select all messages in the category "Updates".
   To do so, you can use the string "category:updates" in the 
   search input text located at the top of the Gmail page.
   Notice the case is irrelevant to the search,
   "category:updates" equals "Category:Updates".

   Gmail then announces "All 100 messages on this page are selected."
   It's not enough, I want all the "Updates" category messages.
   So, on the right of this statement, click on the text 
   "Select all messages that match this search".
   Now Gmail announces "All messages in this search are selected."

3. Apply label "Updates_L" created at step 1 to all the selected
   messages. Gmail will present a warning and a 
   "Confirm bulk action" button. Press "Ok".

4. Repeat steps 1 to 3 for each category you want to synchronize.

5. Transfer your mailbox to the new account with imapsync using the
   options --gmail1 --gmail2, the labels will be synchronized.
   
6. For each of the labels you made for categories, do the steps 7 to 9.
   As an example, I take the label "Updates_L" previously used.

7. Select all messages with the label "Updates_L".
   You can use the string "label:Updates_L" in the search input 
   text located at the top of the Gmail page.
   Gmail then announces "All 100 messages on this page are selected."
   It's not enough, I want all the "updates_l" labeled messages.
   So, on the right of this statement, click on the text 
   "Select all messages that match this search".
   Now Gmail announces "All messages in this search are selected."
   (does it sound similar to a previous §?)
   
8. Apply the category "Updates" to all the selected
   messages. Gmail will present a warning and a 
   "Confirm bulk action" button. Press "Ok".
   If you search where are the categories: the categories are 
   located with the labels, as if they were labels.

9. Delete the temporary label. That part is optional.

Maybe one day Google will make categories optionally available
in IMAP, like any other label and this trick will be obsolete.
Labels can be "Show in IMAP" at
https://mail.google.com/mail/u/0/#settings/labels
Categories are listed there but not possibly "Show in IMAP", not yet :-)

Thanks to Michael Leggett https://twitter.com/leggett for this 
trick. See the story at
https://twitter.com/leggett/status/1484632316697739267?s=20

=======================================================================
Q. The context is a Gmail account at the source, but not Gmail at the
destination. I want cross-duplicates, different Gmail folders/labels
generating duplicate messages across folders on the destination,
except for the "All Mail" folder.

A. This behavior, different Gmail labels generating duplicates across
folders except for the "All Mail" folder, is obtained with a
synchronization with no --gmail1 but instead --exclude "All Mail"
followed by another synchronization with --gmail1 but without
--exclude "All Mail".

  imapsync ... --exclude "All Mail"
  imapsync ... --gmail1

This second sync is done to get the messages with no labels at all
from the folder "All Mail", if they are some of them.

Technically speaking, the first synchronization has not the option
--skipcrossduplicates but the second one has the option
--skipcrossduplicates and it also performs the Gmail "All Mail"
folder/label at the end so only the messages that have no labels will
end up in the "All Mail" destination folder (which is not Gmail,
remember the context).

Thanks to Mike Alexander for this suggestion. 
Mike also provided a patch to implement that directly in imapsync.
See https://github.com/imapsync/imapsync/pull/266
(I refused it because well maintaining it will be very hard for me
and I have other priorities).

=======================================================================
Q. I can't sync more than 1000 messages in each Gmail folder.
   What can I do?

A. It's a Gmail configuration feature that someone set for your
Gmail account. Go to 
https://mail.google.com/mail/u/0/?tab=wm#settings/fwdandpop
and select 
"Do not limit the number of messages in an IMAP folder (default)"

=======================================================================
Q. What are the Gmail imap names of the folders 
   "Sent" "Trash" "Drafts" "Junk" "Flagged" and "All"?

A. By default, Gmail imap names of the folders 
   "Sent" "Trash" "Drafts" "Junk" "Flagged" and "All"
   are like this:

Turned on automapping folders ( use --noautomap to turn off automapping )
Host1: special [Gmail]/All Mail     = \All
Host1: special [Gmail]/Drafts       = \Drafts
Host1: special [Gmail]/Sent Mail    = \Sent
Host1: special [Gmail]/Spam         = \Junk
Host1: special [Gmail]/Starred      = \Flagged
Host1: special [Gmail]/Trash        = \Trash

Host2: special [Gmail]/All Mail     = \All
Host2: special [Gmail]/Bin          = \Trash
Host2: special [Gmail]/Drafts       = \Drafts
Host2: special [Gmail]/Sent Mail    = \Sent
Host2: special [Gmail]/Spam         = \Junk
Host2: special [Gmail]/Starred      = \Flagged

This is an excerpt from the imapsync output log done with the 
--automap option. This listing is located just before the 
folders listings.

This mapping can be changed by configuration in the Gmail 
web interface so the result may vary.


=======================================================================
Q. Can I transfer Gmail "Chat" messages with imapsync?

A. No. 
   Even if you think you can because the Chat folder is seen in IMAP,
   with Chat messages in them, they won't be well transferred.
   Chat messages are not well presented and not well transferred 
   using the IMAP protocol.

=======================================================================
Q. Can I safely use --useuid or --usecache for Gmail transfers?

A. Yes, but I suggest to not use --useuid nor --usecache 
   for Gmail transfers.

Using UIDs is useless with Gmail in the case of global duplicates
(duplicates across different folders). Gmail always accept a global
duplicate message as a new message, giving imapsync a new UID for this
message, and throw it away because it already has it. Gmail
will do this at each run so imapsync will always try to copy the
message, and Gmail will always accept and throw away the new copy. It
ends up with no duplicates on Gmail but a waste of bandwidth and time,
which is the opposite goal of --usecache implied by --useuid.

=======================================================================
Q. Can I use --syncduplicates Gmail transfers?

A. Yes, but Gmail will accept the new duplicate message and 
throw away the new copy. It ends up with no duplicates on Gmail but 
a waste of bandwidth and time.

======================================================================= 
Q. Gmail does not really delete messages in folder [Gmail]/All Mail
   What happens? What can I do?

A. It's true and explained in Gmail documentation at
https://support.google.com/mail/answer/7401?hl=en#zippy=%2Cempty-your-trash

To really remove messages in folder "[Gmail]/All Mail", they have to
be moved to the "Trash" folder and be deleted from "Trash".

Quoting the link above (4 february 2022)
...
Empty your Trash

If you don't want a message to stay in your trash for 30 days,
you can permanently delete it.

* On your computer, go to Gmail.

* On the left side of the page, click More.

* Scroll to Trash.

* Check the box next to messages you want to permanently delete.
  Then click Delete forever.
  
* Tip: The "Delete forever" option is only available in the trash.
  You won’t be able to delete items permanently from the Search result view.
  To delete all messages in your trash, click Empty Trash now.

There is also the Gmail configuration to consider, here is an excerpt:

https://mail.google.com/mail/u/0/?ogbl#settings/fwdandpop
...
IMAP access: (access Gmail from other clients using IMAP)
...
When I mark a message in IMAP as deleted:
	Auto-Expunge on - Immediately update the server. (default)
	Auto-Expunge off - Wait for the client to update the server.

When a message is marked as deleted and expunged from the last visible IMAP folder:
	Archive the message (default)
	Move the message to the Trash
	Immediately delete the message forever

Folder size limits
	Do not limit the number of messages in an IMAP folder (default)
	Limit IMAP folders to contain no more than this many messages
        1,000


=======================================================================
Q. Can I use the Extension of the SEARCH command: X-GM-RAW described at
   https://support.google.com/mail/answer/7190?hl=en
   https://developers.google.com/gmail/imap_extensions#extension_of_the_search_command_x-gm-raw

A. Sure. Example, to search only emails with attachment and in unread state:

On Unix:

  imapsync ... --search 'X-GM-RAW "has:attachment in:unread"'

On Windows:

  perl imapsync ... --search "X-GM-RAW ""has:attachment in:unread"""


=======================================================================
Q. How to avoid the [IMAP] prefix on Gmail side?
How to stop creating folder with this prefix?
Any switch we can use? e.g. [IMAP]/Archive

A. No switch in imapsync since [IMAP]/ prefix is done by Gmail,
   it might be configurable within Gmail parameters configuration.


=======================================================================
Q. Does imapsync have the capability to do 2 stage authentication?

A. No, imapsync doesn't support 2 stage authentication. 
Reading https://support.google.com/mail/answer/1173270?hl=en
it looks like it can't because imapsync uses imap protocol.

So you have to follow the Google recommendation and generate an 
application-specific password or normal authentication 
or use XOAUTH2.


=======================================================================
Q. How to use XOAUTH2 to globally authenticate gmail users?

A. See:
   http://imapsync.lamiral.info/FAQ.d/FAQ.XOAUTH2.txt
   
Really tested on Unix systems, not sure on Windows.

=======================================================================
Q. How to use XOAUTH to globally authenticate gmail users?

A0. XOAUTH is considered obsolete and superseded by XOAUTH2
    See http://imapsync.lamiral.info/FAQ.d/FAQ.XOAUTH2.txt


=======================================================================
Q. How to use a Gmail account to backup several different imap accounts?

A. For each account named xxx use:

  imapsync ... --subfolder2 xxx/xxx

It syncs the account xxx under the sub-subfolder xxx/xxx. 
This way, there is no supplementary label created on the 
multi-archive Gmail destination account. No labels all 
over the place and all original xxx sub-folders show up 
nested within xxx/xxx.


=======================================================================
Q. How to migrate email from gmail to google apps?

A. Take a look at:

http://biasecurities.com/2009/02/migrate-email-from-gmail-to-google-apps/
http://www.thamtech.com/blog/2008/03/29/gmail-to-google-apps-email-migration/

=======================================================================
=======================================================================
