;tldr
Can anyone tell me what’s wrong? Why do emails to a user in my database with an alias domain hit the server but get bounced (and the inbox is not created)?

Background

I have postfix pgsql set up with a PostgreSQL database so that when I add a user (with a @maindomain.com address) in table mailaccounts, they can receive an email. What I want is to be able to add a user in the database with an alias domain like @aliasdomain.com and have that mapped to @maindomain.com. Or in other words, have a user like johndoe1@aliasdomain.com be able to receive emails just like johndoe1@maindomain.com would.

Problem

When I try to send an email from a trusted server like Google to a user in the database (with the alias domain) such as johndoe1@aliasdomain.com, the attempt does hit my server but I get a “user unknown” error.

The main issue is that the virtual alias maps seem to replace @aliasdomain.com with @maindomain.com as intended, but whatever mechanism actually creates the inbox for the new user as would happen if I had sent it to a @maindomain.com user that was in the database.

Postfix logs of error:

Sep 19 02:35:37 mail postfix/lmtp[20721]: 2633A411EC: to=<johndoe1@maindomain.com>, orig_to=<johndoe1@aliasdomain.com>, relay=127.0.0.1[127.0.0.1]:10024, delay=1.5, delays=0.38/0.01/0.01/1.1, dsn=2.0.0, status=sent (250 2.0.0 from MTA(smtp:[127.0.0.1]:10025): 250 2.0.0 Ok: queued as 7210F41237)
Sep 19 02:35:37 mail postfix/qmgr[5088]: 2633A411EC: removed
Sep 19 02:35:37 mail postfix/virtual[20725]: 7210F41237: to=<johndoe1@maindomain.com>, relay=virtual, delay=0.06, delays=0.01/0.02/0/0.03, dsn=5.1.1, status=bounced (unknown user: "johndoe1@maindomain.com")
Sep 19 02:35:37 mail postfix/cleanup[20720]: 8080D41238: message-id=<20220919003537.8080D41238@mail.maindomain.com>
Sep 19 02:35:37 mail postfix/bounce[20727]: 7210F41237: sender non-delivery notification: 8080D41238

Configs

Here are some configs:

MX record of alias domain:
Type Name Content
MX aliasdomain.com mail.maindomain.com

in /etc/postfix/main.cf:

local_recipient_maps =
virtual_uid_maps = static:1001
virtual_gid_maps = static:1002
transport_maps = pgsql:/etc/postfix/pgsql/transport.cf
virtual_mailbox_base = /mnt/mailserver-volume1/mail/
virtual_mailbox_maps = pgsql:/etc/postfix/pgsql/mailboxes.cf
#virtual_alias_maps = pgsql:/etc/postfix/pgsql/aliases.cf
virtual_alias_domains = aliasdomain.com
virtual_alias_maps = hash:/etc/postfix/virtual

in /etc/postfix/virtual

@aliasdomain.com     @maindomain.com

I’ve also run the command

postman /etc/postfix/virtual

to get the virtual.db file for the aliases.