Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the server for the recipient domain xxxx.ru by mx4.xxxx.ru. [xxx.xxx.xxx.xxx].
The error that the other server returned was:
address 188.8.131.52 found in dnsbl.sorbs.net
address 184.108.40.206 found in dnsbl.sorbs.net
Целыми подсетями банят.