My mail server's default configuration uses the
reject_authenticated_sender_login_mismatch setting of
smtpd_sender_restrictions to prevent an arbitrary user A from sending email as user B (in the FROM field). I realize this is generically a good policy, because even one compromised user account would basically open up my mail server as a spam relay.
However, I would like to allow specific users (via a whitelist) to send mail as any user. For example, I would like to have my web server authenticate itself as
firstname.lastname@example.org but then be able to send email on behalf of
All other authenticated users should only be able to send email as themselves.
I think I'm on the right trail with the
/etc/postfix/sender-login-maps.cf file, which currently contains:
dbpath=/home/user-data/mail/users.sqlite query = SELECT permitted_senders FROM ( SELECT permitted_senders, 0 AS priority FROM aliases WHERE source='%s' AND permitted_senders IS NULL UNION SELECT email as permitted_senders, 2 AS priority FROM users WHERE email='%s' ) ORDER BY priority LIMIT 1;
I'm not sure how to modify this to accomplish what I want.