Bingo.

Okay, first things first - go into the UBB's email settings, make sure that each and every option there has a selection (except the SMTP server name, as you're using sendmail) - make sure specifically that the choice between HTML and text email is made - that's when the error you gave occurs.

Question... when the UBB did send mail, did the user receive it FROM administrator@, or is that address only seen when UBB generates errors?

Nice. I changed it from text only to HTML and the registrations email works now. The email of the person who registered did not receive an email though, should it?

The UBB has not sent out any mail that I know of. It seems that the admin email address only pops up when there is an error that it tells the user to report.

Have the user who did not get mail to continue to try to use functions that send mail, such as the UBBFriend feature. Talk to the sysadmins to ensure that the UBB can send mail from the two email addresses listed in the control panel to the user. Sometimes, if a domain is local, sendmail gets a little confused and won't deliver the mail properly unless configured otherwise.

As for the errors... the administrator@ email address was set by the sysadmin... there's nothing you can (or should) do to change it. The best thing to do would be to fix the errors themselves...

Thanks for all the help Charles. Have a good one man.