E-mail Marketing: Avoid Being Flagged as Spam; Update SPF Authentication

* SPF authentication checks appeared in the list of the top 10 content triggers that ISPs check;

* Failing an SPF check proves costly, as it equates to 2.6 points on the current SpamAssassin test, a Bayesian scale that identifies a message as spam when it reaches 3.0 points or greater;

* Marketers sending permission-based e-mails to U.S.-based ISPs still land in the junk/bulk folder almost 16 percent of the time;