When you trying to troubleshoot SMTP delivery issues and using Microsoft IIS SMTP Service. One tip, the logging is not enabled by default. I'm not sure why, but it can provide a ton of great information. Pictures are worth a thousands words. It can be done in three easy steps using IIS manager. So the next time you have mail delivery issues, enable logging, send some test emails and see what is logged. Notepad is a required tool for viewing them. You can even use Logparser to query the files. FINDSTR is my favorite quickie tool to locate information. Impress yourself and your admin with this information the next time you have mail delivery issues.
Note: SMTP Logging is not enabled by default.
Step 1 - Enable logging
Step 2 - this shows where the logs are located
Step 3 - Enable all fields so the maximum amount of information is logged