Need help on this problem "501 Spam Blocked - psmtp"

[nuohai]

Hello smart guys,

I'm sorry that my email server has a problem. Should I look at the configure file of smtp/psmtp? Could you give me any suggestions or answers to similar problem? Thank you so much for your time and help.

Delivery to the following recipient failed permanently:
 
     ***@***.edu
 
Technical details of permanent failure:
 Google tried to deliver your message, but it was rejected by the server for the recipient domain outbounds5.obsmtp.com by outbounds5.obsmtp.com. [64.18.4.12].
 
The error that the other server returned was:
 501 Spam Blocked - psmtp

 

[throAU]

Ensure that you have configured your server to not do the following:

- relay e-mail for third parties
- send backscatter

Ensure that you do not have any infected hosts on your LAN which may be using your SMTP gateway to send spam.