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:

  lucka na berda.cz
    SMTP error from remote mail server after RCPT TO:<lucka na berda.cz>:
    host mx1.active24.com [81.95.97.4]: 554 5.7.1 <lucka na berda.cz>:
    Recipient address rejected: Access denied