As it's been a while since I upgraded (1.1rc10, jump to 1.1.10), this might be present in earlier versions as well.

Anyway, if one enables mail_chroot in global config file, dovecot will try to access /tmp there. Per-user overrides behave correctly.

For example, with:

mail_chroot=/home/vmail

dovecot will abort with:

Fatal: chdir(/home/vmail/tmp) failed with uid 65534: No such file or directory Error: imap dump-capability process returned 89 Fatal: Invalid configuration in /etc/dovecot.conf