Group Emailing

I just got elected to serve as secretary for a group that I'm a member of and part of my duties is to send out emails to all the members. We average about 2-3 emails per month about different events or quarterly newsletters, so it isn't that much work. But, we have a lot of members and the old secretary said they can only send an email to 100 members at a time using our yahoo account. So the same email has to be sent 3-4 times, and you have to remember where you left off the email before so you don't forget anyone or don't send to the same person twice.

I'm looking for suggestions of how to simplify this. I looked into mail chimp which is a free Constant Contact type service, but you have to create the email on their site and use their preformatted newsletters. We have an established newsletter format where we just have to change the wording and pictures that works pretty well. Plus there are a couple of other guys who sometimes send out emails if I can't do it and I don't want to change things up too much for them. Is there a site (free preferred) that just gives me an email address like myclub@3rdpartymailings.com where we could just email that address from our account and it would get to our members? I don't mind adding the names to another site, I'm just trying to simplify how we do it.

Thanks for any suggestions.