Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the server for the recipient domain google.com by aspmx.l.google.com. [2a00:1450:4010:c08::1b].
The error that the other server returned was:
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 http://support.google.com/mail/bin/answer.py?answer=6592 j9si8791583lab.13 - gsmtp
The error that the other server returned was: 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 http://support.google.com/mail/bin/answer.py?answer=6592 j9si8791583lab.13 - gsmtp