There was a lot of worry around the introduction of Gmail's tabbed inbox, and how it'd affect things like open rates. Litmus noticed a drop in opens, and so did the MailChimp delivery team, but the rollout of the tabs was still new, so no solid conclusions could be made.

Tabs have been around for some time now, so our guys went back for another look: How Gmail Tabs Affect Your Email Marketing: An Update We tested with 29 billion emails, and it seems like to have shaken out like this: opens are down, but click rates haven't changed. Better yet, unsubscribes haven’t gone up.

I think it's fascinating that Google (presumably) had the foresight to know it'd go this way. Hopefully, this means the end of the stupid "please move our email into a different tab" call-to-action.