Best way to send out ONE mass mailing to offer opt-in
I have about 50,000 email contacts that I have sent an email to in the past and I'd like to send them one mass mailing offering them an opportunity to sign-up for my Constant Contact monthly newsletter. My question is, how can I reach this size list? I've run into a number of roadblocks so far:
1) I can't send through an email service like Constant Contact because you need permission to send to these many people. (thus why I want to send this first email out in the first place)
2) I was going to do a mail merge with Excel and Google Mail, but I then learned that Google has a block of around 200 emails at once and 500 emails per a day...after that point it shuts down your account for 24 hours.
3) I've thought about going through Mail Chimp, but they explicitely say that you need permission similar to sites like Constant Contact.
4) I've considered hiring someone in India to send out an email to these 50,000 contacts one by one and pay them the $3/hr wage or whatever but this would be WAY pricey and WAY time consuming.
Does anyone have any creative solutions? The goal is to hit the 50,000 contacts with one email explaining that I'm launching a monthly Newsletter and briefly go into the benefits and then offer an email sign-up link at the bottom to clean up this massive list.
Appreciate your thoughts!