Here is a list of points to consider:
1. Does the program allow you to customize your newsletter?
2. Because its free, is there 3rd party advertising on your newsletter?
3. Are you limited in the number of subscribers you can send out or is it unlimited?
4. Will you be able to measure all the analytics? Some questions to ask are:
how many emails were opened, not opened, how many forwarded the email, how
many didn't make it through firewalls, were emails no longer valid addresses
removed from the list? Click-thru rates. This information is crucial to your
5. If your email list is growing make sure the free program can handle expansion.
6. And if something is going wrong, will you have the ability for tech support?
Remember there is no such thing as a free lunch.