This is interesting. sort of.

They only send to me from gmail. Not from a macmail or their own domain. I have a gmail account too. To access it from anywhere on any computer, I have to be on the internet first.......and the From and To fields never change.

Therefore - help me if I'm wrong about this - the only way to change a gmail account's To and From fields, one would have to go into that gmail account and twiddle about (which is a lot of twiddling about) to change anything like that.

Therefore, it doesn't matter whether they're on their iPad or iMac, they're still going onto the internet and accessing their gmail account in order to send me something, right?

Or, could they somehow be using the iPad and iMac to use their macmail to thence access gmail? If yes, how WEIRD is that? How extra-complicated is that? Why do that, that way?

If I'm right, tbh I'm not surprised. One of these correspondents has an intellect rivalled only by garden tools.