My email markup passes the Email Markup Tester, I tried both JSON-LD and Microdata, but no matter what - I just don't see any effect of the markup in Gmail (iOS) client.
Even the basic example from Google's own documentation doesn't work: https://developers.google.com/gmail/markup/getting-started
I'm sending from my own Google account to myself, SPF is functioning.
Anybody ever got this working?
Ok, after trying many different methods I came to the conclusion that the official guidelines don't work (adding SPF and DKIM and sending to yourself), but luckily there is one way to test the markups before applying to Google - using the Apps Script:
https://developers.google.com/gmail/markup/apps-script-tutorial
There is an example of a little script that sends an email on behalf of you. If you put your markup in the message body - you can preview schema.org layouts in action.