Good Email software

hey!

Recently one of our clients change their domain from .net to another one and I need to send an email to a list of 100 clients of them to let them know, I need the email to appear personalized, that the client only sees their email not that the email was send to another 99 persons! Basically I need a program to send massive emails, it´s not for spam purposes is for the reason I just gave.

Any good recommendations? If its free better If I have to pay for it its okay too.

thanks!