I have a SBS 20023.
Server been running for 2 years no problems.
This morning customer rings, internet is slow. I think virus scan all computers, found a few but nothing bad.
Internet still SLOW
So i think hmm maybe server. I stop the SMTP service. Bang internet is all good again. Start the service in a few seconds is't slow again.
I've checked all queues and queue location there is no emails wait there.
It's not relaying problem. This server uses a pop connector to receive emails and port 25 isn't NATed.
I have no other idea what to try. After some help.