 smtp; 550 5.1.1 <ms.rbk@quick.cz>: Recipient address rejected:
    undeliverable address: host 160.218.169.67[160.218.169.67] said: 550 5.1.1
    <ms.rbk@quick.cz>: Recipient address rejected: User unknown in virtual
    mailbox table (in reply to RCPT TO command)
