One of the many things SendGrid does on the backend to determine if a user is having deliverability problems is scan the content through multiple enterprise spam filters multiple times per day for every user.  Some of the filters include Postini, CloudMark, Brightmail, IronPort, Barracuda, Mail Foundry, and SpamAssassin.  These filters are additional filters from our delivery monitory to ISPs such as Hotmail, Yahoo, Gmail, and AOL.  In the last couple of days we noticed that a lot of legitimate emails were triggering the SpamAssassin filter.  The following shows how our graph looks like: (more…)