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:

  martin.born na email.cz
    SMTP error from remote mail server after RCPT TO:<martin.born na email.cz>:
    host mx1.seznam.cz [77.75.76.42]: 550 5.1.1 Sorry, no mailbox here by that name.
  tomas.pavlat na seznam.cz
    SMTP error from remote mail server after RCPT TO:<tomas.pavlat na seznam.cz>:
    host mx1.seznam.cz [77.75.76.42]: 550 5.1.1 Sorry, no mailbox here by that name.
  pan.brm na seznam.cz
    SMTP error from remote mail server after RCPT TO:<pan.brm na seznam.cz>:
    host mx1.seznam.cz [77.75.76.42]: 550 5.1.1 Sorry, no mailbox here by that name.
  peaceboy123 na seznam.cz
    SMTP error from remote mail server after RCPT TO:<peaceboy123 na seznam.cz>:
    host mx1.seznam.cz [77.75.76.42]: 550 5.1.1 Sorry, no mailbox here by that name.
  luky.bob na seznam.cz
    SMTP error from remote mail server after RCPT TO:<luky.bob na seznam.cz>:
    host mx1.seznam.cz [77.75.76.42]: 550 5.1.1 Sorry, no mailbox here by that name.