On my imac 27" 2013, apple mail has a bin. When I delete anything from any of my six IMAP email accounts the deleted mails appear in the top level bin as well as the subsequent account bins within the top level Bin folder.

In my Mail app on my 27" 2013 iMac I have a top level Bin folder, within which are the trash subfolders of all my six email accounts. When I delete any email from any account it ends up not only in its account trash subfolder, but also in the top level Bin folder. All I have to do is click on the top level Bin folder to see all trash emails from all six accounts and delete all contents to dispose of all the deleted emails from all my accounts in one easy stage.

However, Mail on my MacBook Air 2017 seems to want to function in a different way, in that there IS a top level Bin folder with subfolders representing all the trash from all my accounts. But, when deleting any email from any account it will go to the trash folder of the related account but will not be visible in the top level Bin folder. This means that I can't delete all the trash emails from all my accounts in one go from the 'Bin' folder. In fact I have to go to each account trash subfolder to delete them separately, meaning six lots of 'select all' and 'delete' very time.

This isn't the end of the world, but is annoying.

I have tried importing all the settings from my Libray and the Mail preference from the 27" iMac to my MacBook Air and it does NOT cure the issue.

I am running Catalina on both but I had the same issue with Mojave on both.

The settings in Mail/Preferences/Mailbox behaviours are identical on both computers.

On both, Mail/Preferences/Viewing/Move discarded messages into: are set to 'Bin'.

Is it simply that Mail on a MacBook Air operates in a different way? Is it to do with how the app works with different processors (Quad core i5 vs Dual core i5)?........

I'm stumped and would love to kow the solution if there is one.