CRM+Mailer for Nonprofits?

Hey guys I have a question about what CRM software you use. I am in the startup phase of a nonprofit and I would like an automated tool to handle the following:

Take form submissions from website and add to mailing list. Unsubscribe when necessary.

Take form submissions from donation page and send form acknowledging donation at end of year.

Donor tracking workflow for more complex donations like automotive/house.

I have no experience using CRM software. Does anyone have any suggestions or can provide any insight into how your organization uses your CRM system and which CRM you have found most useful? Must have mailer functionality or the ability to integrate easily with a mailer.