Hi Srisailam,
As per my understanding you are getting this error due to mail server configuration issue. When you are trying to call the target server which will send the mail from MII, this server is not relying your MII server and it's return you the error. That might be possible if you are using any public server to send mail. You can do 2 things. 1st you can try to use IP instead of server name. 2nd is, you can try some company mail server or some service provider who allow to use their server to sent mail mostly those are paid service.
Hope it will help you.
Regards,
Suman