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 [126.96.36.199] cmd:
09:57:49 [188.8.131.52] rsp: 500 command unrecognized
How do I resolve this