mail handling question

[Ovidiu]

found this in my mail log:

May 5 14:01:07 h1550830 postfix/smtpd[2167]: connect from server1.nicron.hu[195.70.45.82]
May 5 14:01:08 h1550830 postgrey[2934]: action=pass, reason=recipient whitelist, client_name=server1.nicron.hu, client_address=195.70.45.82, sender=abuse@rum-reisen.de, recipient=abuse@rum-reisen.de
May 5 14:01:08 h1550830 postfix/smtpd[2167]: NOQUEUE: reject: RCPT from server1.nicron.hu[195.70.45.82]: 550 5.1.1 : Recipient address rejected: User unknown in virtual mailbox table; from= to= proto=ESMTP helo=
May 5 14:01:08 h1550830 postfix/smtpd[2167]: disconnect from server1.nicron.hu[195.70.45.82]

why would it say what I marked in red? This is obviously spam... but anyway it never made it into the inbox as the recipient address wasn't yet set up, just wondering...