Data Format Errors using MAIL()

While I found a lot of posts about this problem, I haven't been able to find a solution. So if I missed it, please forgive me, I did spend a few hours trying to find the answer. THE PROBLEM: When a user signs up on a website, an e-mail is automatically sent to them with their password. This worked fine until we upgraded our server to RedHat Linux ES 3.0 using Apache 2.0.46, PHP 4.3.2, MySQL 3.23.58, and Sendmail 8.12.10. Now what happens is that the e-mail is never sent and the following appears in our system logs for each message attempted: ----------- sendmail[4920]: i050MrEq004920: from=apache, size=141, class=0, nrcpts=1, msgid=<200401050022.i050MrEq004920@server1.myserver.com>, relay=apache@localhost sendmail[4920]: i050MrEq004920: to=me@myserver.com, ctladdr=apache (48/48), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=30141, relay=[127.0.0.1] [127.0.0.1], dsn=5.6.0, stat=Data format error sendmail[4920]: i050MrEq004920: i050MrEr004920: DSN: Data format error sendmail[4922]: i050Mr1J004922: <apache@server1.myserver.com>... >apache<@myserver.com. sendmail[4920]: i050MrEr004920: to=apache, delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=31165, relay=[127.0.0.1], dsn=5.3.0, stat=User unknown sendmail[4922]: i050Mr1J004922: from=<>, size=1165, class=0, nrcpts=0, proto=ESMTP, daemon=MTA, relay=localhost [127.0.0.1] sendmail[4920]: i050MrEr004920: i050MrEs004920: return to sender: User unknown sendmail[4922]: i050Mr1L004922: <postmaster@server1.myserver.com>... >postmaster<@myserver.com. sendmail[4920]: i050MrEs004920: to=postmaster, delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=32189, relay=[127.0.0.1] [127.0.0.1], dsn=5.3.0, stat=User unknown sendmail[4922]: i050Mr1L004922: from=<>, size=2189, class=0, nrcpts=0, proto=ESMTP, daemon=MTA, relay=localhost [127.0.0.1] sendmail[4920]: i050MrEr004920: Losing ./qfi050MrEr004920: savemail panic sendmail[4920]: i050MrEr004920: SYSERR(apache): savemail: cannot save rejected email anywhere ----------- I have NO idea or clue where to start looking or what is causing the problem. If anyone else has had this problem and fixed it, I'd really appreciate hearing from you! Thanks - Monty