This documentation is for Dovecot v2.x, see wiki1 for v1.x documentation.


WARNING: Badly done migration will cause your IMAP and/or POP3 clients to re-download all mails. Read Migration page first carefully.


By default UW-IMAP allows access to whole home directory. Since the home directory may contain many other files as well, many people have chosen to store their mails in the mail/ directory. This usually means that IMAP clients have been configured to use mail/ as their "IMAP namespace prefix" (the clients use different names for this). This doesn't work with Dovecot, because Dovecot shows clients only the mail/ directory instead of the whole home directory. So if the IMAP namespace was kept as mail/, Dovecot would try to access the ~/mail/mail/ directory.

There are three ways to fix this:

  1. Remove the IMAP namespace prefix from the clients.
  2. Use namespaces to allow users to keep using the prefix. See "Backwards Compatibility" in Namespaces for an example configuration.

  3. Configure Dovecot to use home directory (mail_location = mbox:~/:INBOX=/var/mail/%u and set mail_full_filesystem_access=yes). The latter is needed to make ~/mail and ~user/mail prefixes work.

A typical mailbox location setting is:

mail_location = mbox:~/mail:INBOX=/var/mail/%u

~/mbox file

If a ~/mbox file exists, UW-IMAP moves all the mails from /var/mail/user into the ~/mbox file. Currently Dovecot doesn't support this feature. There are two possibilities to handle this:

(There is also a plugin, Plugins/Snarf, which can emulate UW-IMAP's behavior.)


UW-IMAP keeps the list of subscribed mailboxes in ~/.mailboxlist file, while Dovecot keeps them in ~/mail/.subscriptions file. UW-IMAP's subscriptions also contain the mailboxes with their prefixes, for example:


UIDs, flags and keywords

Dovecot uses UW-IMAP compatible metadata headers in mboxes, so it's possible to migrate back and forth without losing any flags, keywords or cause IMAP UIDs to change.


UW-IMAP uses dotlock + flock() as the default locking combination, while Dovecot uses dotlock + fcntl() by default. See MboxLocking to determine what are the correct lock settings for you. To use UW-IMAP compatible locking, use:

mbox_read_locks = flock
mbox_write_locks = dotlock flock


The first message in a mbox file may contain the subject "DON'T DELETE THIS MESSAGE -- FOLDER INTERNAL DATA". This system message has information about the mailbox and its state.

Dovecot v1.0 uses these system messages. Keep them.

Maildir conversion

If you're planning on migrating to Dovecot, you might also want to switch to Maildir format as well. However it might be easier to first migrate from UW-IMAP + mbox to Dovecot + mbox, and only then migrate the users to Maildir format.

UW-POP3 (UW-IMAP's POP3 wrapper, ipop3d)

By default Dovecot generates POP3 UIDLs differently than UW-POP3, which causes POP3 clients to redownload them as new messages. You can avoid this by setting:

pop3_uidl_format = %08Xv%08Xu

To utilize the UW login conversion to lowecase, we recommend that you use the following option:

auth_username_format = %Lu

You can confirm that the old and the new UIDLs match:

telnet localhost 110
user test
pass test

None: Migration/UW (last edited 2019-10-30 12:28:03 by 139)