Take this advice with a grain of salt... (the above post take with an iron clad fist and believe it)
I have a dedicated server for just sending emails, well also backups, errr.. also host a couple sites on. But anyhoo...
I use this dedicate server and create sub-domains on it... i.e.
mailer.barefootsiesisapig.com
I then send emails from that server using...
http://www.phplist.com/
It is totally free and my host set it up.
Be careful about how many emails are sent per hour and you should be ok. If you get a good host, if your IP becomes blacklisted for whatever reason, just put the emailer sub-domain on a different IP and carry on.
Emailing consultants are likely some of the biggest frauds out there.