i got below maintained error:

shashi.fresher2014@gmail.com on 3/27/2015 9:32 AM
  There was a SMTP communication problem with the recipient's email server.  Please contact your system administrator.
  <infosys-exchang.infosystest.com #5.5.0 smtp;550-5.7.1 [121.244.168.94      12] Our system has detected that this message is>

Check if your IPS DNS servers are listed on your Local DNS and are set as your Forwarders? If yes, change it to the Global DNS Server and flush the records and then re-register the DNS. Once you are done with this, your problem will get resolved.

Hi,

In addition to the above suggestion, I would like to clarify the following thing:

Please check if your public IP is listed in the blacklist by this recipient's email server.

What's more, it is recommended to upgrade your Exchange server. Since Exchange 2003 is old Exchange version, we have not supported for Exchange 2003. Your understanding will be appreciated.

Hope this can be helpful to you.

Best regards,

Hi Shashidhar,

Your mail pointer 121.244.168.94 (mail.sonatasoftware.com) must have some getway to send mail in external domain. From that getway you need to check that are you able to ping 8.8.8.8 or not. If yes than check the recipient ID is valid or not. And if you are using Exchange environment than you need to check the Outbound SMTP mail flow go to this Link :-

https://testconnectivity.microsoft.com/

After it collect the debug log share it on the forum and will get the solution.