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:

  krtej na email.cz
    SMTP error from remote mail server after RCPT TO:<krtej na email.cz>:
    host mx1.seznam.cz [77.75.78.42]: 550 5.1.1 Sorry, no mailbox here by that name.
  vasekm3 na seznam.cz
    SMTP error from remote mail server after RCPT TO:<vasekm3 na seznam.cz>:
    host mx1.seznam.cz [77.75.78.42]: 550 5.1.1 Sorry, no mailbox here by that name.
  dj.b na seznam.cz
    SMTP error from remote mail server after RCPT TO:<dj.b na seznam.cz>:
    host mx1.seznam.cz [77.75.78.42]: 550 5.1.1 Sorry, no mailbox here by that name.
  studentzr na seznam.cz
    SMTP error from remote mail server after RCPT TO:<studentzr na seznam.cz>:
    host mx1.seznam.cz [77.75.78.42]: 550 5.1.1 Sorry, no mailbox here by that name.
  hobojka na centrum.cz
    SMTP error from remote mail server after RCPT TO:<hobojka na centrum.cz>:
    host cax.virusfree.cz [31.7.241.25]: 554 5.7.1 <hobojka na centrum.cz>:
    Recipient address rejected: Access denied, user does not exist