Answer
There are a variety of reasons why this may be the case including your license, disk fragmentation, threads, server load, network traffic, hard disk issues, or anti-spam settings. One issue in particular that was causing trouble was that GMS was doing a lookup on all mail passed via SMTP regardless of whether it was local or not.
We have changed this and SMTP now only does a lookup where the RCPT is local.
See Also:
- Why is Virus Scanning slow with inline scanning enabled?
- Can I slow SMTP responses to bad commands?
- What is contained in release 3136?
Keywords:smtp slow delay incoming