My Client is having issues with his email. My smartermail (server) is based at Singapore. When I perform a self test at my computer, everything is working fine.
However in China, my client is unable to send. I checked the smtp log and saw a 500 command unrecogized.
09:57:49 [18.104.22.168] cmd:
09:57:49 [22.214.171.124] rsp: 500 command unrecognized
How do I resolve this