Ninety seven out of 100 email-sending IP addresses' reputations are bad enough that email providers would likely block their messages, according to an email study.

A mere 0.9 percent of IP addresses score high enough to ensure that emails they send would likely be delivered, according to a study by email deliverability services firm Return Path, Directmag.com reports. Luckily, most commercial marketers' IP addresses are within that 0.9 percent. However, their "Sender Score," as monitored by Return Path, tends to be closer to the borderline 70 than the highest-level 100.

Return Path uses six criteria (e.g., complaint rates, email volume sent, unknown-user rates) to assign each address a 1-100 score. Senders with scores above 70 would likely have their email delivered; those below 30 likely wouldn't. The highest-scoring IP addresses tend to be corporate accounts that don't send much email and don't spam.

"Most marketers are between 60 and 80," George Bilbrey, general manager of Return Path's delivery assurance solutions unit, is quoted as saying. "Most marketers are in the gray area. The question is: How gray are you and how can you get yourself to a lighter shade of gray?" The answer lies more in reputation and less in email content, he says.