I was about to answer this, but decided I didn’t want that information in public.
However, the bank I use, which is a largish one, has an app that I’ve installed with the aurora store without microg or google play services on divestos and it complains that it won’t work without gsf, but it works fine after clicking ok.
This is a comment from someone who has no idea what DKIM is.
Those emails were cryptographically proven to be sent from that email server.
Saying anything else proves you are ignorant of the technology and trying to provide cover for emails that were proven to come from the DNC servers at a mathematical level.