How can I test outgoing e-mail?

The Test Mail Server Tool that you mentioned before, works great for testing. If I would set my provider's smtp settings in php.ini, then the mails would actually be sent to the recipients, wouldn't they? With the Test Tool, that's not the case, and I can check the lay-out and contents of the mails without bothering anyone.
Only (small) problem is that some characters are being replaced by equal-signs.