Why don't you right click the message and use Move To and then use delete and Trash as intended?

Airmail said

Why don't you right click the message and use Move To and then use delete and Trash as intended?

It's exactly what I'm doing since I discovered the issue, but the problem seems to be the delete feature.

I also tried to set the setting "When a message is delete" back to "Mark as deleted", but I always get the same result: the email loose all the labels and Gmail moves it to the "All Massages" directory.

There is no problem. Delete is delete, regardless of the folder used the command to the server is delete. GMail in their non standard implementation use all mail as an archive, so deleted mail automatically gets archived as it is deleted.

I really do not understand what your trying to achieve with a "new" trash folder. What is the point?

Matt said

I really do not understand what your trying to achieve with a "new" trash folder. What is the point?

It all started because I want to delete messages from my trash after more than 30 days and, as far as I know, there's no way to force Gmail deleting emails after ore than 30 days.

Do you have an hint for how to do so?

Right click on gmail 'Trash' fodler and select 'Properties' click on 'Retention policy' tab uncheck 'Use my account Settings' select; Delete messages more than eg: 30 days old click on OK

re: gmail All Mail and deleting info:

• https://support.google.com/mail/answer/78755?hl=en
• https://support.google.com/mail/answer/78892?hl=en