Multiply MailingManager Description:
This gem allows you to create an Unlimited amount of mailing lists that can hold an unlimited amount of subscribers.

Allows you to collect subscribers with a traditional subscribe box OR by sending a blank email to ANY POP3 e-mail account. Not just your domain POP3 access, but also the free ones.

And Installation is super easy. Just change ... WholeSomeSoftware LLC. (download page)