CRM and newsletter integration?

I already use WordPress to create an online catalog and web presence. Now, a little box tells people to enter their email address, and they will receive an email when a new product is added to the site (which is useful).

Now, having entered the email addresses manually or asked people to enter it, I would like to have a little CRM for managing those mails, getting the names, phones, emails, addresses, and references (why they are in the database) - all in WordPress.

So when new content is added, or when I would like to send all those people info (mass mailing), I can use the same system as for managing my site.

What solutions have you tried and used for this?