Webinar Roundup: Building Your E-mail List

As for that burning "how much e-mail is too much?" question, Karp said you won't know that you're sending too much e-mail until people complain or cancel their subscriptions. But given that, if you have no complaints or unsubscribes, you might not be sending enough e-mail. He recommends sending more rather than less, as it's likely busy recipients won't open all of them anyway.

Once you've got a good list and a good message that's spam-proof, don't stop there. Hone both with constant testing and experimentation in the form of A/B testing and segmentation.

A/B testing is a side-by-side comparison of two e-mails with different versions of one element, whether it's the subject line, message length, header information, etc. The key is to only test one element at a time and keep the e-mails as consistent as possible. Split your e-mail list in half and send the tests at the same time. And be sure both e-mails have a call to action that can be measured.

"Don't have one message that's got a different subject line and a different length and a different call to action, or you won't really be able to tell which of those things that you were playing with had the best effect," he noted.

Segmentation involves separating out groups within your e-mail list (new members, or donors above a certain dollar value) and sending them a more tailored message that relates to them more specifically. Be sure to test the messages you send to your segments to make sure they're having the desired effect.

"Remember, the more tailored, the more personalized, the more customized a message is, the better people tend to feel about receiving it. So a generic newsletter that everybody gets is certainly helpful, but it doesn't bring a whole lot of clickthrough and action," Karp noted. "Whereas a letter to a donor that specifically recognizes the amount of their last gift and requests another gift is going to do a lot better."