19% of email addresses provided in free offers are bogus.
Service Objects has a corporate client that gave us approximately 120,000 email addresses from various campaigns and on various dates in 2011. Each address was processed through our email validation service. Each address was checked for syntax, domain-level validity and mailbox-level validity; additional checks for vulgar and bogus addresses were also performed.
At first glance the addresses looked OK. They were properly formatted and their domains (right side of the address) mostly belonged to the top e-mail providers like gmail, Yahoo, Hotmail and others. However using email validation tools, we determined that 18.7% (22,700 out of 120,000) had mailbox level errors. These email addresses are undeliverable because the mailbox element (the left-side of the address) is no longer a valid working mailbox.
An example of one of these addresses is: firstname.lastname@example.org. The address has good syntax, a working MX record, a valid SMTP server but the mailbox element (cgommer) is invalid according to cox.net. Perhaps this entrant made up this address? Perhaps she moved ISPs? There is really no way for us to know with 100% accuracy. This was a bad address and should have been marked in their database as so.
Why valid email addresses matter: Marketers who look to re-connect with clients need valid working addresses. Email service providers like Constant Contact and MailChimp have rules in which they seek a maximum allowed bounce-back rate of only 5%*. If your bounce-rate is too high (>5%) you will be banned from mailing with their service. They do this to weed-out poor quality lists and to reduce load on their mail servers.
What you do about it: Marketers seeking to improve their email address quality should take the following actions:
(2) use a hosted email validation tool
(like those we offer at www.serviceobjects.com)
(3) send a confirmation email to verify users identity
(4) should periodically re-validate the list prior to any bulk mail campaign