RFM as it is understood by direct marketers is not applicable to email marketing.  However, RFM is applicable for Email.

RFM is so effective in direct mail because it identifies the breakeven point of sending mail pieces. It tells you who not to send to.  Arthur Middleton Hughes, a pioneer in the direct marketing industry, has a blog post on the topic over at Silverpop.

Of course, he’s right. You shouldn’t apply RFM the same way you’d apply it for direct mail. What we have learned at Top Right is that RFM is applicable in triggered emails. R – recency – has long been understood as the most powerful indicator of a subsequent purchase – driving up lifetime value. We apply that learning from the direct marketing industry to drive our clients to use triggers to their most recent customers. Those work really, really well.