Sendmail is what I would've figured too except this is on a vanilla Ubuntu (Dapper server) install with no MTA (including sendmail, pear or postfix) added.
Is sendmail somehow bundled into PHP with a different name perhaps?
Sitting at the root prompt in /, issuing find -name 'sendmail' returns no results..
Sorry, this is more a curiosity to me than an actual support issue, phpBB is purring like the sleek, sexy kitten is is. I just have an (external) dev that is pushing me to install an MTA (sendmail) so she can mail form results and I'm telling her to get bent because the phpBB install I put on is sending mail just fine.
She's figured out I need to edit php.ini to point it to sendmail but... sendmail 'aint on the server and with it being Dapper (and out of the loop on repository updates) I'm definitely not adding anything more to it.
I'd love to be able to tell her how to code her script. Or at least point the way for her but.. well, I'm a little perplexed too since I haven't been able figure out how phpBB is doing it either. At least, not yet.
Doesn't help that I haven't really had my hands in this box since putting it out there 5 yrs ago or so but phpinfo does tell me that it has Zend extensions installed.
So...... - I'm guessing thats what phpBB is using since no other MTA is installed?