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:

  tizanek na sezna.cz
    SMTP error from remote mail server after RCPT TO:<tizanek na sezna.cz>:
    host sezna.cz [46.28.105.4]: 554 5.7.1 Service unavailable; Client host [62.36.20.214] blocked using dnsbl.sorbs.net; Currently Sending Spam See:
    http://www.sorbs.net/lookup.shtml?62.36.20.214
  jipjop377 na gmail.com
    SMTP error from remote mail server after RCPT TO:<jipjop377 na gmail.com>:
    host gmail-smtp-in.l.google.com [74.125.206.26]:
    550-5.2.1 The user you are trying to contact is receiving mail at a rate that
    550-5.2.1 prevents additional messages from being delivered. For more
    550-5.2.1 information, please visit
    550 5.2.1  https://support.google.com/mail/?p=ReceivingRatePerm l10si12315128wrc.360 - gsmtp