I set up a customer's Exchange mailbox so that they could use an application
to retrieve and parse e-mail in a mailbox via POP3. I set up the following
security related measures.
- Required 128 bit SSL and used the existing certificate in place for OWA
for the POP3 virtual server.
- Restricted only the server running the application to be able to access
POP3 on the Exchange server.
- Restricted only the mailbox being accessed from being to use POP3.
- Restricted the number of possible connections to 5.

This was working last week and then suddenly stopped this week. We were
seeing errors like:
Socket connection was aborted by remote host

I turned up diagnostic logging on POP3 which only yielded
Event ID 1004 "Closing connection to "

Also, I saw a few of the following errors:

Event Type: Warning
Event Source: POP3SVC
Event Category: Configuration
Event ID: 1055
Date: 8/7/2007
Time: 12:27:55 PM
User: N/A
Computer:
Description:
The server certificate for instance '1' could not be retrieved because it
could not be found in a certificate store; the error encountered was
'0x80092004'

I'm not sure what the possible causes of this error are normally but I
removed all my security configurations and set them back up and then the
application started working properly again and was able to authenticate to
the mailbox, retrieve messages, etc.

Does anyone know the possible causes of the errors generated above? One
item I noticed was the customer was using the actual servername of the
Exchange server instead of that on the certificate in his code. That said, I
got him to change that but it didn't make any difference until I reset
everything.

Archived from group: microsoft>public>exchange2000>connectivity