I've got a client with SBS2008 6GB RAM Exchange 2007 SP3 - which i just updated
The server keeps complaining about Mail Submission , and mail flow stops until your restart Mail submissions and transport services.
Restarting the server makes not difference
I've checked and there is no back pressure, the RAM usage is slighty high 82%
The Microsoft Exchange Mail Submission Service is currently unable to contact any Hub Transport servers in the local Active Directory site. The servers may be too busy to accept new connections at this time.
Service MSExchangeMailSubmission. Unable to process anything for over 30 minutes. Diagnostic info: Governor: Governor for DatabaseManagerEvent, Last run time: 02/09/2016 13:02:20, Next retry interval: 00:05:00. Current exception: Microsoft.Exchange.Assista
kit, InterestingEvent interestingEvent)
I have increased Concurrent connections but that makes the situation worse
Any other ideas?
6GB of RAM is woefully underpowered for SBS
My first two recommendations
1. Run the Fix My Network Wizard
2. Run the SBS 2008 Best Practice Analyzer