[Dovecot] best choice of user database file to work with postfix?

[Thomas Leuxner]

I'm running a setup that should be good enough for what you are trying to achieve. All user information is stored in flat files per domain and you may override per user settings individually:

passdb {
  args = username_format=%u /var/vmail/auth.d/%d/passwd
  driver = passwd-file
}

userdb {
  args = username_format=%u /var/vmail/auth.d/%d/passwd
  driver = passwd-file
}

$ cat passwd 
user at domain.tld:{scheme}<password>:5000:5000::/var/vmail/domain.tld/user::userdb_quota_rule=*:storage=5G userdb_acl_groups=PublicMailboxAdmins

I would vote against storing aliases in these files though. Reason being the Postfix alias files are more flexible, because you would need to setup NULL password/No Login users or similar in the Dovecot backend. Another reason to keep them in Postfix is to completely separate alias management from the user management and use the same for login checks.

See how aliases are used for routing and to authenticate valid mail from senders with one file:

$ cat virtual
alias at domain.tld                login at domain.tld
postmaster at domain.tld           login at domain.tld

[main.cf]
virtual_mailbox_domains = domain.tld, domain1.tld
virtual_mailbox_base = /var/vmail
virtual_minimum_uid = 100
virtual_uid_maps = static:5000
virtual_gid_maps = static:5000
virtual_alias_maps = hash:/etc/postfix/virtual
virtual_transport = lmtp:unix:private/dovecot-lmtp
[…]
smtpd_sender_login_maps=hash:/etc/postfix/virtual

If this seems suitable I can send more details to you.

Regards
Thomas