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:

  lenka.novotna na cezdistribuce.cz
    SMTP error from remote mail server after initial connection:
    host smtp12.cez.cz [89.111.77.165]: 554-smtp12.cez.cz
    554 Your access to this mail system has been rejected due to the sending MTA's poor reputation. If you believe that this failure is in error, please contact the intended recipient via alternate means.