Avoid the Delete Key

According to an eROI consumer survey, 56 percent unsubscribe because they’re receiving e-mails too frequently from marketers. This impacts the quality and size of the list.

A quick analysis of subject lines and content from those catalogers who mail three times a week shows that there’s nothing extraordinary about these e-mails. They’re just more of the same offers and promotions I’ve already received.
The Curse of Broken Links
Nothing will turn your customers off more than when they’re interested in an item, click on the link and get a “page not found” error message. Overcome this by testing all the links in your message prior to sending.