The last time I engaged this problem is messily documented at:
The description of hat usage case, however, was complicated by the fact that I was copying messages into another gmail account. Hoping to re-confront a similar problem under a simpler usage context.
I am accessing my gmail account over IMAP using Outlook 2019 desktop installation (not Office 365 Outlook web app). I use the All Mail folder almost exclusively, as it lets me see both sent and received messages. I'm very diligent in deleting messages and threads, including messages whose text are contained in the email trails of later response. I delete such messages by dragging them into the Trash folder.
When I look in the Inbox folder, however, many messages are present which are not in All Mail. Some are plain email messages, some are appointment invites, and others are appointment acceptances. Using the Gmail webmail interface, I ensured that the Inbox's "Social" and "Promotion" message bins were empty, then resync'd all folders over IMAP. Therefore, the explanation cannot be that messages in "Social" and/or "Promotion" show up in the Outlook Inbox folder and not the All Mail folder.
All the time spent ensuring a clean unbloated mail account has been wasted. My Inbox seems to be littered with messages that I supposedly cleaned out. It would take a lifetime to go through that vetting process again.
What am I doing wrong? How can I properly delete messages from All Mail without creating this nonsensical disparity with Inbox?