"Google is currently failing emails sent to Gmail accounts if they are signed with a 512-bit key or less. Now there is evidence that Google is starting to enforce their policy of accepting DKIM keys of 1024-bit or higher."
"Currently, there’s no such thing as “mobile email standards.” But that doesn’t mean can just wing it—not when 70% of consumers say they delete emails immediately if they don’t render well on their mobile device.
The more you know about what limitations exist, the better off you’ll be. Here are some quick tips to get you headed in the right direction:"