[Exim] unexpected disconnection while reading SMTP command

Dear List,

Our domain not able to received email from remotehost.com.tw and below
is the only related message I can see:

Aug 16 13:21:16 ms1 exim[20635]: 2004-08-16 13:21:16 unexpected
disconnection while reading SMTP command from (e250.remotehost.com.tw)
[211.72.XXX.XX]:22309

Any guide what to do?

Note: We can still send email to them (remotehost.com.tw); only
receiving is the problem.

Thanks in advance.

Sean