[Trent Adams]

I can’t see how bbPress would be any different than wordpress in terms of the mail usage, so:

Emailed passwords not received

Description: When users try to register with your blog or change their passwords by entering their username and email, WordPress says that their password has been emailed to them, but it’s never received.

Reason and Solution: WordPress uses the standard php mail function, which uses sendmail. No account information is needed. This is not generally a problem if you’re using a hosting service, but if you’re using your own box and don’t have an SMTP server, the mail won’t ever send. If you’re using a *NIX box, you should have either postfix or sendmail on your machine; you’ll just need to set them up (google for how-to’s). If you don’t want to go through setting up a complete mail server on you *NIX box you may find ssmtp (http://packages.debian.org/stable/mail/ssmtp) useful – it provides “A secure, effective and simple way of getting mail off a system to your mail hub”. On a Windows machine, try a sendmail emulator like Glob SendMail (http://glob.com.au/sendmail/).

More help can be found on the forums at: https://wordpress.org/support/topic.php?id=24981

Translation, there are posts in the normal wordpress.org forums as well that even dreamhost for whatever reason doesn’t send the passwords out through sendmail. I would look in the dreamhost support as well, maybe an answer is right there for you to grab

Trent