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:

  iloveyouworldmyfriends na gmail.com
    SMTP error from remote mail server after RCPT TO:<iloveyouworldmyfriends na gmail.com>:
    host alt2.gmail-smtp-in.l.google.com [142.250.150.26]:
    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 p13si13950540lfo.210 - gsmtp
  njoye na libimseti.cz
    SMTP error from remote mail server after RCPT TO:<njoye na libimseti.cz>:
    host mail.libimseti.cz [109.123.202.56]: 554 5.7.1 <out12.wanadoo.es[62.36.20.214]>:
    Client host rejected: Greylisting in effect, sending server blacklisted