There is nothing in accounts-advanced that selects where incoming mail should go. Also nothing in Mail settings. So what do we do now?
There are a number of posts on this but no real solution.
IOS 8 and 12 tried.
Do you have vacation mode turned on in iCloud Mail? Or are you forwarding your emails to a different email address?
Log into iCloud>Mail. At the bottom left is a gear icon. Click on that and select Preferences. Under General is the forwarding preference. Uncheck that. Next check the Vacation preference and undo that.
Anything in common with the emails that go to the trash? same sender, or something else that would somehow identify those "trash" emails? Are ANY of the trashed emails from senders in your contacts/address book (or NONE of the trashed emails are in your contacts?)
Or, only those in your contacts go straight to trash, etc? Anything like that?
More than likely it is a mail rule that has been set up for that particular email address that is putting them in the trash. Do you just use your phones for emails, or do you have a desktop/laptop as well?