mail settings for primary domain

[maur]

Let's say my domain for server, admin panel etc is: admin.r.pl
Now i see in logs:
Feb 12 01:28:05 r postfix/smtp[6069]: 074C1347BE: to=<webmaster@admin.r.pl>, relay=none, delay=0.03, delays=0.03/0.01/0/0, dsn=5.4.6, status=bounced (mail for admin.r.pl loops back to myself)

I tried add admin.r.pl as domain, but then Im getting:
Feb 12 01:11:25 r postfix/trivial-rewrite[5724]: warning: do not list domain r.pl in BOTH mydestination and virtual_mailbox_domains

Do you have any ideas..?