While most e-mail marketers think forbidden content is usually why their e-mail gets blocked from recipients, senders' bad reputations are responsible the vast majority of the time, according to deliverability concern Return Path.

When commercial e-mail gets blocked, the senders' reputations were responsible 77% of the time and the reputations of the domains included in the e-mail were responsible 6% of the time, according to a recent study by Return Path.

The company conducted the study as part of an effort to tout its latest e-mail deliverability tool: Sender Score Resender.

Set to be available to Return Path's Sender Score clients in November, the new service allows marketers to send e-mail messages that showed poor delivery rates a second time from clean IP addresses to some test e-mail accounts at most major inbox providers. Messages reaching the inboxes on the second send mean the sender's IP addresses are the source of the delivery problems, according to Return Path.

Internet Service Providers use recipient complaint rates as the No. 1 factor when determining whether or not to block incoming e-mail from specific senders.

"Most marketers believe that they can tweak content and see deliverability rates increase, that by taking out the words 'free' or '10% off', their emails will suddenly make it into the inbox," says George Bilbrey, vice president and general manager of Return Path's Delivery Assurance division, in a statement announcing the new service. "We have long held that a marketer's reputation with receivers is the reason for poor results, and now with Resender we can easily prove it."