I would recommend using a script on a web server to send the e-mail in batches, usually 50 emails per batch tends to work quite well for me.
I'll assume you're using PHP and MySQL but if you're not then I'm sure your developers will be able to convert the idea easily enough.
>establish a connection to the database
>Use a for loop to iterate 50 times
>>pull a record from the database where the person has not already been sent a mail
>>construct a mail to the recipient
>>send the mail
>>make a record that you haven't sent the mail to that person
>>wait for a small amount (25ms works for us)
>wait a few minutes before running the script again
I don't know how much mail you have to send but we only have to send 600-700 mails and this solution seems to work for us.
And Zarn: Grow up. The majority of "spam" is issued by botnets whereby the software creators are already capable of far more advanced solutions than "sending lots of emails". There are plenty of reasons to send mass e-mails to people.