Google is sending mass scale notifications via email and Webmaster Tools warning sites that are not mobile-friendly that it will cause issues for them if they want to rank well for smartphone users.

This is the first time Google is sending these notifications to these webmasters. We reported on this last week but I thought that site had a mobile design and had issues with it. The truth is, the site was not mobile friendly at all and now many sites like this are in the same boat.

Typically, Google only notified sites that were supposedly mobile friendly, when it has mobile usability issues. But now, it seems like the algorithm they may have been testing around mobile ranking might be going into affect in the near future.

For Google to send out these warnings in mass scale, it kind of implies this might be coming.

Here is a copy of the "Fix mobile usability issues found on..." email that several of my clients, who have old, non-mobile friendly sites, received over the weekend:

Forum discussion at WebmasterWorld.