Someone I regularly receive mail from has an address of the form forenamesurname@aol.com or ForenameSurname@aol.com, depending (I think) on which device they us

Someone I regularly receive mail from has an address of the form forenamesurname@aol.com or ForenameSurname@aol.com, depending (I think) on which device they use. Gmail will treat one as spam, but not the other. To stop the trapped emails ending up in the spam folder, I had to create a custom filter: simply marking mails as 'not spam' in the spam folder does not do the job. And the filtered mails now have a yellow banner plastered across them saying "This message was not sent to Spam because of a filter you created." I'm going back to Mutt and my ISP's mail server.