Every few months or so, I like to send out an e-bulletin to forum members. However, the vBulletin built-in script just isn't robust enough as it constantly will time out every few pages. I've also tried sending mail directly from Mirosoft Outlook, but the sheer volume of emails made that nearly impossible as well.
I'm looking for a mailing list script that will let me throw a good 20K addresses at it - and it will run behind the scenes on my server. In other words, I don't want the actual sending to be via a web application that can continuously time out - nor do I want to have to keep a webpage open for so long.
A couple of years ago I was writing a program to do just this, send out the monthly news letter for the ecommerce company I was working for. I wrote it in C and linked to libesmtp, it was a very easy task, perhaps you should look at doing something like this? The application I wrote read a file that had the content of the email and another file with a delimited list of names and email addresses it would then use substitution to replace keywords in the email and send it to the address, it took about a week to write and handled about 500K of addresses, it also worked in such a way that it didn't force too much load on server itself. I also had to mess about with sendmail to reduce the timeout value for none responsive addresses.
Failing that an easier solution could be to use mailman and create a mailing list that can only be posted too by the admin, this is a webbased frontend but the backend isn't.
DadaMail - I could not ever get installed on my server [ Perl Scares Me too Much ;) ]. But I have heard realy-really good things about it. Try it and see if you can get it installed...
PHPList - Excellent Piece of Work... But whenever a new release is there , it is usually followed by 3-4 more releases. If you can keep up with that , then its perhaps even better than the commercial scripts available.
As far as Mailman is concerned - its what SlashDot and RedHat use to manage its own list [ so you know that its reliable ] . But , Its written in Python [ IMO ] . Its more of an email discussion list but can be hidden in one way or other to behave as an announcement list. I have the documentation but never actually needed to start a list. If you want I can pass em over to you.