We (that be me:) will be release a evaluation license for a home based sales market. The evaluation system will be available from our server at some point.

When prospects install the evaluation copy they would need (nice way of saying "forced") to register for an activation key that would allow them an evaluation license.

This is my sketch for the initial evaluation release "activation". At "first" run time:
1) The application would generate a class key and write it to a field at the users desktop.
2) A routine similar to "SENDSMTP" would email the program's support email account (that be me) and the prospect/user registering for activation an email with the class key/activation code.
3) The prospect would then enter that "key" and be allowed an evaluation period.

My questions are:
1) Is SMTP a "a mail from anywhere / anytime" guy? Is SMTP a ghost (does he leave stuff in the default mailers output box).
2) The source of the email will be the users "desktop". Can I falsify the "From" address with the "support" (that be my email account) - I think this can be done with SMTP - but is it acceptable [even] for a single, tiny benign email?

The goal is to make it appear that an autoresponder generated or fetched the key, thus: forcing them to register. Once the user selects to send their registration, they will be prompted to check their inbox for their activation key.

Any advice appreciated - thanks