by Kirill Popov

A recent report on email false-positive rates by email deliverability firm Pivotal Veracity gives a slight edge to senders who use double opt-in to add addresses to their mailing lists. But results also showed using the double, or confirmed, opt-in method won't guarantee that all emails will go straight to the in-box.

The study found that 54% of the 100 companies scored false positives when sending email to leading Web-based email services. (A false positive is an email message from a requested sender that was wrongly tagged as spam and sent to a bulk folder.)

Among the findings:

1. Only 18 of the senders used double opt-in as a means of attracting and confirming subscribers.

This is considered the gold standard in both collecting good addresses and in preventing people from being subscribed against their will. The good news, though, is that only one sender used opt-out to add names to its lists, meaning 81 senders used some form of single opt-in.

2. Double opt-in mailers had a better chance of staying out of the junk folder, but this approach doesn't guarantee that what they send will always go to the inbox.

The study found 61% of email messages from double opt-in mailers went to the inbox, compared with 41% of those from single opt-in mailers. However, that still means 39% of a double opt-in company's messages would up in the junk folder, with 59% for single opt-ins.

3. Crucial transactional messages such as subscription confirmation, confirmation requests and welcome messages wound up identified incorrectly as spam for almost one-third of double opt-in companies.

4. Third-party accreditation services not only didn't stop email from being marked as spam, they also might have made the problem worse.

While 53% of email from companies that pay for third-party service went into the junk folder, TrustE clients saw 57% diverted, with 55% for Bonded Sender users.

5. Companies that outsourced their email deployment had a slightly lower false-positive rate (48%) than those doing email in-house (43%).

To collect data, Pivotal Veracity opened free email accounts at Yahoo! Mail, MSN/Hotmail and Gmail. Employees then subscribed to email content -- newsletters, announcements and offers -- from 100 U.S. senders including non-profit agencies. (No email was received at any of the accounts from 10 companies.)

The firm monitored the senders' permission practices and whether email landed in the inbox or was classified as spam. The study didn't count any email messages sent to only one or two accounts, instead of all three accounts, because it was not clear whether the sender excluded the service on purpose or the service blocked the email message.