What's The Perfect Frequency of Marketing Emails?

Like everything else in marketing, it depends.

Due to its generally low cost, e-mail lacks the economic discipline of traditonal offline direct marketing media (direct mail for example). Thus the temptation is to overuse the medium.

Conversely, many marketers are perhaps overly concerned about frequency. Many sought after prospects receive hundreds of emails daily, so the chances that you’ll wear out your welcome are often exaggerated.

Again, as in all things marketing, your mileage may vary. The best thing is to test frequency on a ceteris paribus (all other things being equal) basis and use the results to guide your tactics