email messages to one recipient being rerouted elsewhere

Thanks for your reply Mac Jim ID. Looking around MY Gmail/Google security screens, I didn't see anything suspicious including any other devices or sessions or any recent activity that I didn't recognize. I sent a message from Gmail on Google and it didn't appear in sent on my MAC mail program, but was received as expected on another device, so if someone had my Gmail password and sent messages from there, they must have already deleted them. I've changed my password, added 2FA, and there's only me signed on to Google at the moment, so I don't think I can do anything else here.

I don't think your last suggestion about the different email address will help. The phony messages I got always had the correct full email address of the person I was expecting. I thought perhaps the small "L"s in the email address might have been changed to "I"s like Iowa or ones but I copied the address from one of the phony messages to Word and changed the font to one with serifs and that was not the case. I typed the full address name@first-last-name.com on my last message and sent it while I had the recipient on the phone. It did not arrive. Any further ideas or comments?