My Advice: Leave it to the experts
As someone who has set up their own PHPList, GroupMail, and several other products and projects... let me give you one piece of valuable advice.
If you're looking for the "brain damage free" solution go with a 3rd party provider such as "Constant Contact":
I personally have not used them but several of my clients do and LOVE it. For myself, I continue to use GroupMail and PHPList to send out thousands of newsletters but let me tell you... that's after YEARS of struggling and fighting to get it all "dialed in".
First of all... make sure you're CAN-SPAM compliant (assuming you're in the USA).
Second... make sure your IP address is static and has a reverse DNS for the IP.
Third... make sure your mail server is properly configured... and by properly I mean SERIOUSLY properly configured... not just something that sends out email.
Fourth... make sure your ISP knows who you are and what you're doing. Many ISPs have policies build into their TOS to deal with people who send bulk email... even opt-in newsletters. Just because you're CAN-SPAM compliant and have the user's permission doesn't mean your ISP will like you. I'm on a first name basis with most of the tech guys from my ISP.
Fifth... be prepared to fight every little "wanna-be" blacklist in on the internet. Some don't matter... some do. If you end up on them... its sometimes a complete pain to try and get OFF them.
Sixth... clean your email list! Process those bounces. The big guys will ban you quickly if you start sending to too many "bad" email addresses.
Seventh... get signed up with the "big boys" as far as bulk mail and understand how they work.
Eights... I can go on and on... but I think you're getting the idea...
If you have a client and he only wants to email 8,000 people... you're probably WAY better off going with someone like Constant Contact (or someone similar) and letting THEM deal with any potential brain damage.
Keep it simple. :-)