[Mailman-Developers] Recipient address rejected: User unknown in virtual alias table

[Danil Smirnov]

Now I have working Postorius and I can subscribe myself to the test
list and get the welcome message (with incorrect urls in it!).

But I could not post to the list or mail to the list owner from outside:

550 5.1.1 <test-owner at domain.tld>: Recipient address rejected: User
unknown in virtual alias table

I've checked postfix/main.cf and everything looks right in it.
Also I've ensured that var/data/*.db files are world-readable.
Selinux is disabled.

How could I debug this error?

Thanks,
Danil