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:

  r.kamos na sznam.cz
    SMTP error from remote mail server after RCPT TO:<r.kamos na sznam.cz>:
    host sznam.cz [46.28.105.4]: 554 5.7.1 Service unavailable; Client host [62.36.20.208] blocked using bl.spamcop.net; Blocked - see https://www.spamcop.net/bl.shtml?62.36.20.208
  patriot999 na nam.cz
    SMTP error from remote mail server after end of data:
    host mail.nam.cz [185.241.242.243]: 550 5.7.1 This message is blocked due to security reason