I am running php on a linux server using apache and sendmail.
When I try to use the mail function sendmail does not appear to send the email (yes sendmail is up and running fine - it delivers email from other mail programs).
When I check the logs I see an error "Unkown User" in the log entry for the email I am trying to send.
Any idea why this is happening or how I can fix it?
This is all just a guess.
When a user connects to your Web site, what account does that run under? nobody? guest? wwwuser?
Find that out, and make sure that the user is authorized to send mail via sendmail.
Again, just a guess. Hope it helps.