[Dean C]

Don't waste your time with a) vBulletin's mass mailer and b) Some dodgy exe program

I remember doing some work on a forum with around 10k members about a year ago, and we had a nightmare trying to send emails out to our members letting them know that the site was under new ownership and had new a new design/forums etc. The main problem is that hotmail, gmail, yahoo were all flagging the emails as spam and they never reached the user's inbox.

The first thing you should consider is if you're running a shared host. If you are, then you have little chance of getting your IP address whitelisted as a safe sender as other people on your IP can abuse it. Secondly, if your IP address falls within a range where there are other bad servers (perhaps your host has, in the past, provided dedicated boxes to people who have abused them) then you're going to have a hard time getting your mail through.

But ultimately, you need to get in touch with the big mail providers and especially Hotmail to go through a long approval process involving tweaking your server config and filling in forms.

Sending mail is not as simple as it used to be. Good luck with doing it from your own solution, but my advice would be to use CampaignMonitor. They have done all of this already and are whitelisted and take out the hassle of doing it yourself.