[thelist] Best PHP Email Newsletter Application

[Tony Spiro]

I have two email lists, a 3000 + email list and an email list of 600 users
registered on my website.  I have just recently started sending two weekly
newsletters one to the large email list and the other to the 600 +users,
both with a hand-coded while loop and mail() function.  For about two weeks
the 600 user list was working great, and now it's not working.  This is my
first attempt at my own email newsletter application, needless to say, it's
having some problems:

--It is really slow!
--It only sends out about 150 to the 3000 + email list

Can someone please tell me what my best option is for a PHP email newsletter
application for my site.

Thanks in advance,
Tony