An alternative to PHP's mail() using SMTP?

Oh boy.

I just discovered, after mucking with sendmail logs for a while, that the reason many of my password notification and other emails aren't coming through to users is that mail servers on the receiving end are discarding my messages based on their source IP range (my client has hosting through Webstream, apparently they've had some naughty customers).

Now I am trying to figure out a way to allow Drupal to send emails without having to rely on PHP's mail() (and thus on the local sendmail, which doesn't work because of this IP range deal).

I'm wondering if anyone has experienced similar problems and has figured out a good solution. The only thing I can think of is to use my host's SMTP server instead, but the SMTP module appears that it may be dead, and only has a CVS snapshot for 5.x from back in June.

Can anyone offer some advice?

Thanks a bunch,
Ben