E-mail Based

Email RSS Aggregator - Service offering updates delivered direct to an e-mail inbox.

Feed2Imap - A feed aggregator that can download feeds then uploads them to a specified folder of an IMAP mail server.

Feed2Mail - A service that converts an RSS feed into a mailinglist that people can subscribe.

Newspipe - An RSS/Atom aggregator which allows the user to keep track of feeds through e-mail.

RSSknip - A subscription service that tracks user selected keywords over a range of feeds.