We use a service that continually monitors our mail servers’ IP addresses and alerts us if we show up on any blacklists. This helps us respond quickly to any deliverability problems that could potentially jeopardize our customers’ campaigns.
Anyway, this particular service will also monitor other IPs that don’t even belong to MailChimp, even though I never told it to (long story). An interesting side effect to that feature is that I got an alert today telling me that one of Google’s email servers is on the SORBS blacklist, for sending email to a spam trap (learn what a spam trap is, and how to keep them off your list).
Here’s a screenshot (click to zoom):
Ouch. My guess is one of their users sent an email to a very, very, very old email address that’s been turned into a spam trap. Or, a spammer hacked into Gmail (see article below) and sent spam to a huge list tainted with spam traps.
The lesson here is that if Google is vulnerable to blacklisting, anybody is. Do you know if your list is vulnerable? Here’s a guide to help you find out.
On a related note, Ars Technica reports: Gmail being throttled, blocked by some anti-spam vendors