hi there
how may emails are you thinking of sending in one go ??
you will find that many email servers reject bulk email sends, and bounce them back to you, therefore you need to use an online company such as mojomail, or livewire but there are loads of companies,
you can import your database to your account, and then the system will monitor the unsubscribes, etc.
you can then create a template or a plain text email, select the receipents and then send, some companies charge £5 per campaign and then 1p or 2p per email sent.
if you have a website, then if you have a data capture box, you can then add them to the subscribed list.
ideally you can have a microsite that acts as a landing page back from the email.
you may also be asked by the companies whether you have permission from the reciepents to receive email marketing.
on a positive note, a lot of compaies now prefer to receive marketing by email as opposed to hard copy.
regards
martin