inbox@inbox.gmrservice.ext.google.com
...
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 fl6si3394876qcb.0 - gsmtpAnyone knows what that "rate limit" is?