Mail doesn't Erase Deleted Items and other problems

Here's what I tried in the meanwhile...

1. Preferences, iCloud, unchecked Mail
2. Closed Mail.app
3. Finder, Library, Mail, trashed V5 folder
4. Opened Mail.app
5. Result: Only Inbox and Sent mailboxes show in left panel
6. Preferences, iCloud, checked Mail
7. Status bar said it was downloading messages, Drafts mailbox showed up in left panel, no other folders
8. Closed Mail.app and opened it again
9. Result: Same problem, no Trash mailbox and I can't delete trashed messages

I think this requires a reinstall...

Here is a screen grab of second problem. Note the line under the first email. It is selected and has the body of another email. I don't have threads or conversations or anything else turned on; just one message at a time. And I can't delete it.

Thanks for any help.

I followed your instructions:

1. Set Trash mailbox to iCloud, there is no Trash folder that shows up, but a Deleted Messages folder showed up in the left panel under iCloud. I had one deleted message in there; shows up in Trash on iCloud Mail.
2. Safe Booted, had a different problem: I could not delete the message in the Trash mailbox, but the "ghost" mail was gone.
3. Rebooted normally: same problem, could not delete the message in the Trash mailbox, no "ghost" mail.
4. Disconnected from the internet, Mail.app did not crash when I clicked Erase Deleted Messages, but it still has the problem that the message in the Deleted Messages folder does not erase; no "ghost" mail.
5. Quit Mail.app and logged in to iCloud, Mail, there were no later emails than the one's I've been working with. But there are just four emails total, if that helps. No "ghost" mail.
6. I have just one IMAP account, Rebuilt the mailbox.

Okay, just got a new email, deleted it, but it never arrived in the Deleted Messages folder under iCloud folder in the left pane of Mail.app and it is not in the Trash folder on iCloud Mail.

Summary: Mail.app does not crash when I click Erase Deleted Messages, but the deleted messages don't erase. And the "ghost" message is gone; I think the Safe Boot solved that.

Any more ideas?

Thanks.

I started going through the Menu choices, and when I click View, Show Deleted Messages, I see a different set of deleted messages, but the highlighted mailbox in the left pane is the Inbox. Very strange. I thought reinstalling High Sierra would fix this, but now I'm not so sure.

Yes, WebMail at iCloud.com has a Trash icon as in your screenshot.

I reinstalled, but there's no Trash on the side panel in Mail.app. I changed the Preferences, Mailbox Behaviors, Trash to iCloud. But when I close Preferences, and reopen it to check, Trash mailbox is set to None.

I checked WebMail on iCloud and there are the same emails in the Trash folder. And I can delete them; empty the trash. They go away in WebMail and...checking Mail.app, they are gone there too.

I sent a test email to myself. I can delete it, right-click delete, but there is no option to move it to Trash, just delete.

Update: I checked preferences again and there was no Trash folder selected. Here's what I see:

Another observation, I am not positive, but I thought I had a Trash folder in the left pane of Mail.app. It was Inbox, Sent, Trash, and Junk. I am not sure if I can use Time Machine to verify that.

Okay, I do not have Trash on Mail.app, in the left side panel. It sounds like another reinstall of High Sierra. Is there another way to get the Trash back?

Thanks!