SendEmail is a great little SMTP Windows command line tool
I've been working on a Subversion post-commit hook that will send me an e-mail when a user checks in some code to a repository. In order to send an e-mail from the post-commit script I needed a command line tool that would let me send an SMTP message from my batch file.
Fortunately for me, I stumbled upon SendEmail by Brandon Zehm.
This program is chock-full of features and is the perfect companion for Subversion for Windows installations. I can also see this being an extremely useful general debugging tool as it as you can create some really complex e-mail scripts.
SendEmail is actually a Perl program but has been compiled into a native Windows executable. You can download the Windows executable in two flavors—with or without TLS support.

Comments
http://www.blat.net/
BTW, I think the phrase you wanted is "chock full of features". I suppose it could be a localized difference in vernacular, but just in case I thought I'd mention it.
http://www.wsu.edu/~brians/errors/chalkfull.html
Thanks for the correction. Spelling has never been one of my strengths.