Question
GMS Mail only delivers mail to A record of domain, it does not appear to do any MX lookups in the post log.
Answer
Make sure your domain is specified in your Network Control Panel, TCP/IP settings.
If you do not specify your domain name in the TCP/IP properties for Windows NT, GMS Mail will not attempt to resolve the MX record for a remote domains. Instead, it will attempt delivery to the A record.
See KB 373 for more details on delivery rules.
Keywords:post, A Record, delivery, outgoing, queue