Blasting 100K emails, lol.. I'll assume you bought them from some non-legit company. You cannot buy targeted city e-mails for REAL people for under $1K/10,000. Or did you spend, $10,000 on 100K e-mails? If that's the case, no company can truly deliver that many, ie you are talking 50%+ of the cities population's e-mails. 50%+ can't have opt-ed in to something like that. Even the most reputable companies, have limits, a few of the top companies I've been speaking with are peaking at 16K-20K email per my city/surrounding area. Also even if you paid $300 for 100K and think you got some great deal, remember 100% of those e-mails are scraped or resold from older lists, and not to mention they've been spammed to death. There's no point in even buying those, you just wasted 100% of your investment from the start.
Besides the point.
If you are sending out 100K emails with a service like constant contact or mailchimp (I use mailchimp), you will be banned and have your account terminated. Reputable e-mail senders for bulk campaigns are very picky about the # of complaints for SPAM they get. If you send out 100K there's no doubt you'll get your account terminated. Even if you could get away with it the first time, you're looking at $500/MIN to send it out.
Now if you have to ask for a company that can send those out as well, chances are you going to look for anyone that will send it out. And you're going to go through less legit channels and end up with some company that will fail to deliver those messages to the inbox due to their lack of management and high volume of complaints.
In short this is just a bad idea.. There's much more to e-mail than meets the surface.