I noticed today that an e-mail that I had sent on 18 Nov 2017 and which was replied to on 20 Nov 2017, suddenly showed up in my Inbox. I had previously moved it to a local folder (back in November). The only thing that MIGHT be related is that I had sent a message yesterday to the person who was cc’d on the return e-mail of the November message. I had NOT opened the November e-mail and the subject of the November e-mail was different than the subject of yesterday’s e-mail. That November message does NOT appear when I open Gmail on the web, so it seems to be an eM Client issue only. They need to fix this issue of phantom e-mails showing up in the inbox INCLUDING (from another of my posts) the issue of a copy of e-mails moved to local folders showing up in the trash.
If you moved the November email to a local folder, it will not be visible in the web interface for your account.
Robert, can you disable conversations in Menu > View > Conversations > Disable Conversations, and verify where the phantom message is.