From White Peak Software:
SMTP Diagnostics is a program that assists with troubleshooting problems that can occur with outgoing mail (SMTP). You can send a test message, with or without attachment(s), and view the protocol messages exchanged between your computer and the mail server. This information can help you analyze problems or can be passed on to technical support personnel. Version 1.7 adds improved support for Vista.
What's new in this version:
Version 1.8 added timing option to profile and total elapse time.