Content is a primary factor in inbox placement. Testing against spam filters simply isn’t enough these days, because the ISPs are more sophisticated. Send yourself test messages in each of the major email clients and tweak it until it gets though. This will help you figure out the root of your problem.
For more information on the role of content in inbox placement, click here http://www.slideshare.net/emaildelivered/role-ofemailcontent.
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