#!/bin/cat
$Id: FAQ.Dovecot.txt,v 1.19 2025/09/12 12:52:23 gilles Exp gilles $

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


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      Imapsync tips for Dovecot. Specific issues and solutions.
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Questions answered in this FAQ are:

Q. Is there imapsync specific options to deal with Dovecot?

Q. The login fails with the error:
   Err 1/1: Host2 failure: Error login on [...] with user [...] auth [LOGIN]: timeout waiting 120s for data from server (5x)
   What can it be?

Q. Character not allowed in mailbox name: '.'

Q. Subfolders are not created by imapsync and the error is
   "Mailbox doesn't allow inferior mailboxes"

Q. How to migrate to Dovecot with an admin/MasterUser account?

Q. I have a mailbox that "dovecot backup" gives errors on that
   I can't get rid of: "UID inserted in the middle of mailbox".
   What can I do?

Q. Imapsync encounters timeouts and Dovecot log says
   "mailpiler dovecot: imap(xxx): Error: Timeout (180s) while waiting for dotlock for transaction log file ..."
   What can I do?

Q. I have this APPEND error:
   Err 98/100: - msg INBOX/277 {29390} could not append ... Flags:[\Seen blob ] ) ...: 280 BAD Error in IMAP command APPEND: 8bit data in atom .
   What can I do?

Q. Imapsync transfer only a subset of folders from host1.
   What can I do?


Now the questions again with their answers.

=======================================================================
Q. Is there imapsync specific options to deal with Dovecot?

A. Dovecot is ok with imapsync, nothing special is needed, just the
   basic options, ie, the credentials, are needed.

=======================================================================
Q. The login fails with the error:
   Err 1/1: Host2 failure: Error login on [...] with user [...] auth [LOGIN]: timeout waiting 120s for data from server (5x)
   What can it be?

A. It can be special characters in the password. Change it with only
   normal characters, characters from a-z A-Z 0-9

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Q. Character not allowed in mailbox name: '.'

A. Depending on the Dovecot configuration, the dot character "."
   can be special and not allowed when used as a separator, either
   inside on the file-system, or outside as the IMAP separator.
   
   Solutions, either:
   
   1) Change the folder name at the source account, replace all dots
      by another character like _ or - or whatever.

   2) Tell imapsync to change it, the following 
   
       imapsync ...  --regextrans2 "tr,.,_,"

    will transform any . to _

   3) It should be possible to allow the dot in folder names with some 
      Dovecot configuration.

     Searching for the issue, I came across
     https://forum.hestiacp.com/t/character-not-allowed-in-mailbox-name/566/2
     which is a good read to understand the issue, and maybe fix it.

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Q. How to migrate to Dovecot with an admin/MasterUser account?

A. Dovecot uses the same syntax as uw-imap

  imapsync ... --user2="loginuser*admin_user" --password2 "admin_user_password"

To setup a Dovecot MasterUser follow the document
https://doc.dovecot.org/configuration_manual/authentication/master_users/

If you encounter this error message from imapsync:
Err 1/18: Host1 Folder INBOX: Could not select: 16 NO [SERVERBUG] Internal error occurred. Refer to server log for more information.

See then:
https://github.com/imapsync/imapsync/issues/148#issuecomment-1982241694

I quote budiantoip
```
This happened because I use a master user to transfer the mailboxes, 
and the master user does not have access to the user's mailboxes. 
The solution is to modify the dovecot config and add these 2 lines:

plugin {
    # lines of the existing plugin block
    ... 

    acl_user=%u
    master_user=%u
}

Save the changes, and validate the config with this command:
    doveconf >/dev/null && echo OK
If it returns no error or warning messages, restart the dovecot service. 
You should be able to proceed after that.
```

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Q. I have a mailbox that "dovecot backup" gives errors on that
   I can't get rid of: "UID inserted in the middle of mailbox".
   What can I do?

A. Solution, run:

  doveadm -v deduplicate -m -u martin mailbox A/Posted

it will get rid of the duplicates (it can also be run without "-m")
and this also allows "dovecot backup" to work.

Thanks to Martin Ward for this input!

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Q. Subfolders are not created by imapsync and the error is
   "Mailbox doesn't allow inferior mailboxes"

A. Dovecot usually supports subfolders with messages and subfolders,
   it's a Dovecot configuration issue.

If you can change the Dovecot configuration dovecot.conf, 
then try this:

mail_location = maildir:~/Maildir:LAYOUT=fs

See details at:
https://superuser.com/questions/813362/sub-folders-in-dovecot
https://wiki2.dovecot.org/MailLocation/Maildir


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Q. Imapsync encounters timeouts and Dovecot log says
   "mailpiler dovecot: imap(xxx): Error: Timeout (180s) while waiting for dotlock for transaction log file ..."
   What can I do?

A. It looks like an NFS issue with Dovecot. 
   Solve it with Dovecot support or use something else than NFS.
   I'll be glad to share here any solution you find.
   (Thanks to Mate Skoblar for reporting this issue)

=======================================================================
Q. I have this APPEND error:
   Err 98/100: - msg INBOX/277 {29390} could not append ... Flags:[\Seen blob ] ) ...: 280 BAD Error in IMAP command APPEND: 8bit data in atom .
   What can I do?

A. Use this to remove all 8bit characters from the flags:

  imapsync ... --regexflag "tr [\x80-\xff] []d"

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Q. Imapsync transfer only a subset of folders from host1.
   What can I do?

A. Answer from Ionel Spanachi

I noticed that imapsync would transfer only a subset of folders from
host1. After investigating, I found out that the fault (of course) was
on the archaic dovecot-server. When listing folders of a user via
master_user access, it would show only shared folders, INBOX and Sent
and imapsync would accordingly and naturally transfer only folders
shown in response of the LIST command.

Dovecot has a file in ~/Maildir/dovecot-acl-list, which for unknown
reasons does not get updated automatically. Removing this file for
every user suddenly exhibits ALL the folders, which are then correctly
identified and processed by imapsync.  I'm doing something like this
now:

migrate-single-mb:
 
#!/bin/bash
 
if [ -z ${MASTERPASS} ]; then
     echo "MASTERPASS no set!"
     exit 255
fi
 
DOVECOT_HOME=$(doveadm user -u $1 -f home) || { echo "User [$1] has no home!"; exit 1; }
 
DOVECOT_ACL_CACHE=${DOVECOT_HOME}/Maildir/dovecot-acl-list
 
if [ ! -f $DOVECOT_ACL_CACHE ]; then
     echo "$DOVECOT_ACL_CACHE not found."
fi
 
rm -f $DOVECOT_ACL_CACHE

# Check, if folders now appear as they should:
echo -e "a1 login $1*virtual $MASTERPASS\na2 LIST \"\" *\na3 LOGOUT" | openssl s_client -connect localhost:993 -crlf -quiet | grep -v shared

imapsync --host1 localhost --user1 ${1}*virtual --password1 "${MASTERPASS}" \
         --host2 192.168.110.21 --user2 ${1}*masteruser --password2 "${MASTERPASS}" \
         --exclude '^shared\.|^shared/' \
         --delete2 \
         --nolog

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