We have an Exchange 2010 behind a NAT, port 25 is forwarded to the exchange server.
Everything was running well. But today, I noticed that nobody is no longer receiving emails from outside the organisation.
When I send a test message from any other account (hotmail, gmail, another exchange organisation) I never get any rejection or delayed delivery notification. But in my mailbox, there are only messages coming for colleagues in the same organisation.
I used (Tracking Log Explorer) in EMC to see all messages today (about 100 nos), and found all of them are coming from senders in ourorganisation.com domain.
How to track and troubleshoot what is going on our email server?