I am not from any hosting company you can check their SMTP ips at this website our mail are bouncing when we sending to our clients and we receive error "Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 550 550 5.7.0 Your server IP address is in the Backscatterer Blacklist database, bye (state 14).
"
Here is the blacklist checking url
Backscatterer.org powered by UCEPROTECT
These are the google apps IP address SMTP servers
209.85.212.183
209.85.212.202
209.85.212.172
Just check it whats this....