[CentOS] Postfix and virtual mail boxes.

Rob Kampen
Thu, 07 Oct 2021 05:18:07 -0000

Hi, not sure this is the best place to go for my problem, but hoping
someone can point me to the correct or better place.

I have two currently working CentOS 7 based email servers that host a
number of virtual domains and users and delivers mail just fine - for
correctly addressed vmail inboxes AND for alias addressed emails and
domains.

These all use postfix, dovecot, amavisd, clamAV, spamassassin, mysql
(mariadb) and roundcubemail

I use port 25 for the world email delivery - no auth needed as only
accepts hosted virtual domain addressed email.

and

port 587 for user client MUA to send mail - smtp with STARTTLS auth needed

port 993 for MUA IMAP access to account mail boxes

A couple of weeks ago I rolled up a new minimal virtual server (also
CentOS 7) and basically copied the same setup as the other two and have
now spent far too long trying to get it going.

My initial problem was that I? set up mydestination to include $mydomain
- this has the consequence of seeing any mail@$mydomain as local email
and trying to deliver to the local machine rather than the vmail inboxes.

So after setting up a new domain just for the MX we moved on.

All three installations use mysql (mariadb) as the data store for
domains, alias domains, user vmail accounts, and forwardings (virtual
alias mapping)

The mysql bits work just fine as I can send mail from an MUA client and
they deliver correctly via an authenticated session on port 587 - i.e to
any world email address AND to local vmail boxes, including those
addressed via an alias and/or alias domain.

What fails to work on the new installation, but works fine on my two
legacy servers, is mail addressed via an alias. Specifically an alias
domain. Even adding the complete alias email address to the forwardings
table doesn't work.

e.g. let's say we have an email domain '@example.com' and an alias
domain '@example.org'.
Needed so I can migrate my clients from one server to the other in a
staged manner.

Thus the new server is set up to operate as the MX for @example.org and
@example.com but needs to alias redirect the incoming emails being sent
to fred at example.org and deliver them to the vmail location for
fred at example.com (i.e. we have no vmail locations for @example.org only
for @example.com

So if I send a test email via my MUA (using port 587 and hence
authenticated) it does the alias lookups and translations needed and
correctly delivers the mail.

However if I send an email to fred at example.org from say a gmail account,
it arrives at my new server and promptly gets bounced with a 550 5.7.1
error - no such email address.

After doing diff on the main.cf and master.cf from all three servers the
only differences are the myhostname, mynetworks (new one is dual stack
IP4/IPv6 and thus includes [::1]/128), smtpd_tls certificate names, and
the virtual_uid_maps - all expected and accounted for.

master.cf are identical

Many dozens of google searches and reading far too many pages, has left
me with no idea why my new server doesn't accept alias directed emails
via port 25.

All the documentation indicates that alias lookups and translations are
performed by postfix - all the time.

receive_override_options is not set.

Any suggestions of things to check or test would be welcome.

TIA
Rob