The findings, part of the latest Lyris EmailAdvisor ISP Deliverability Report Card, show that ISPs in Canada present marketers with even more of a challenge as Canadian ISPs were found to label as junk or spam more than 14 percent of the permission-based e-mails.

The Report Card also showed that, of the 25 United States ISP that were studied, some of the most popular providers turned out to be the most likely to route the messages to junk or bulk mail folders instead of inboxes.

Google's Gmail deep-sixed 28 percent of the messages while Yahoo sent to the spam bucket 19 percent and Hotmail disposed of 16 percent. "Noticeably absent from the top ten ISPs with the worst inbox delivery is AOL, which ranked 14th on the list with a junk delivery rate of only 2.33 percent," noted the study's authors.

There is no easy way for marketers to prevent their legitimate e-mail pitches from suffering the same fate as unwelcome Viagra solicitations, get-rich-quick scams and other spam, said Stefan Pollard, director of consulting services at EmailLabs.

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