If you prefer not to pass this out to someone to do it for you then you have two main options:
1. Run the email campaign in house using a purchased desktop / server software system
If you have the necessary in house resource, then buying a system could be an option but do make sure that the software supplier includes upgrades in the purchase price. The market is still developing and the services offered are getting better as well as prices coming down.
A couple of suppliers that offer a service worth looking at are given below, but it is worth comparing the services they offer as this will change, particularly in the tracking arena:
Broadcast (from a company called MailWorkz)
Gammadyne
Lyris
When considering this option, elements that you will want to bear in mind are your internal capabilities in terms of designing the email and working with the software, and your IT set-up including whether bulk email going out through your ISP is something that they will be open to, together with the online processing of bounced emails, unsubscribes etc.
2. Run the email marketing in house and use a hosted / online system
This is probably the simplest method in terms of IT set-up although there is still a learning process with regard to learning the system you select. The system is hosted externally by a company specialising in email marketing and you pay a monthly charge to use the system - this charge is generally either dictated by service level, size of mailing lists or number of emails sent. It is good to check the exact charge configuration if cost is a major issue.
You would import the contacts from your own database or Excel spreadsheet (usually through a CSV format). create the emails within the system and then send out the campaigns from there. Some will offer tracking as part of the package while others offer this as an upgrade so it is worth checking it out if tracking is a key element to your campaign. Some recommended suppliers offering this set-up are:
Constant Contact
Mailer Mailer
AWeber
Vertical Response
If you are combining two or more lists, then you may also wish to consider cleaning the list of email addresses before using it. The basic action will be to de-dupe it, which means to remove duplicated addresses or multiple addresses for the same person. Most of the email marketing systems will have a simple de-dupe facility which is probably all that you need once the system is automatically adding email addresses, then again all of them should do verify current addresses on an ongoing basis before adding a new one.
If you have an old list or are unsure about it, then it would probably be wise to verify the recipients as a double opt-in if you want to do this properly, which is what I would recommend.
Good luck with it all.