After having purchased the catastrophic competitor Worldcast, I switched to Mach5 Mailer and it worked like a breeze. Mach5 Mailer is extremely powerful, and the good news are that if you don't need the advanced features, they won't come in the way.
I was able to use various SMTP servers with lots of constraints thanks to the advanced options (you can limit the flow right under your allowance for example). The tech support seems great (1st question answered right away, on a Saturday !).
For $99, I didn't dream getting that many features.
The Gold version, more expensive has practically unlimited power dues to scripting support, but it's definitely not for beginenrs. The regular registered version is just perfect even for quite complex mailings.
I strongly recommend this tool.
Review details