Mail delivery failed: returning message to sender

[Mail Delivery System]

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

  vajda na labcontrol.cz
    SMTP error from remote mail server after RCPT TO:<vajda na labcontrol.cz>:
    host mail.labcontrol.cz [90.176.152.243]: 550 5.1.1 Mailbox <vajda na labcontrol.cz> does not exist