FP does allow you to specify the email address that you want to display on your outgoing email. Setup for it may vary by email client. I use Mozilla Thunderbird and by clicking on "Tools" and then choosing "Account Settings" go to "Outgoing Server (SMPT)." Next to the SMPT settings click on "Edit". In the "Description" box type in the desired email address that you want your email recipients to see. Outlook Express is probably very similar in its setup.
I went back and tried again (Outlook Express), and after some dinking I discovered I had to turn on outgoing authentication for FP's SMTP server. Once that was turned on then FP's SMTP server would accept something other than @myfairpoint.net in the sender's e-mail field. Thanks for prodding me take another look.
Of course, it would have been nice if the FP tech that I spoke with on Saturday knew that answer ...
