I'm finding a fair amount each day (~50 - 100) messages in my Exchange queue that puzzle me. (Please see screen shot).
The "FROM" address is blank "<>"
The subject always has "Undeliverable" next to it.
I'm trying to figure out if it's
1. A bounce back. Spam to a non-existent user and this is the bounce back to a non-existent domain it's trying to bounce back to.
2. Is someone connecting directly to port 25 of my server, like a command line thing and trying to use the server as an open relay? I've checked and double checked, the server isn't an open relay.
3. Something else?
I think it's #1 but I'm not sure.
Any ideas whats causing it and how to stop it?
ALso, next to "Message Source name" is says "DSN". What is DSN?
As always, thanks!