Emails from multiple accounts go to the same trash folder

Question

I use Emacs and mu4e for email. I set up multiple accounts as in the manual. I also included this snippet from here to send deleted messages to a folder instead of deleting them permanently:

(add-to-list 'mu4e-marks
     '(trash
       :char ("d" . "▼")
       :prompt "dtrash"
       :dyn-target (lambda (target msg) (mu4e-get-trash-folder msg))
       :action (lambda (docid msg target) 
                 (mu4e~proc-move docid
                    (mu4e~mark-check-target target) "-N"))))

The problem is that all deleted messages are marked to go to the Trash of the main account instead of the Trash of their own account. Running help on key d shows:

d runs the command mu4e-headers-mark-or-move-to-trash (found in
mu4e-headers-mode-map), which is an interactive compiled Lisp function in
‘/usr/local/Cellar/mu/1.4.1/share/emacs/site-lisp/mu/mu4e/mu4e-headers.el’.

It is bound to d, .

(mu4e-headers-mark-or-move-to-trash)

which in turn shows:

mu4e-headers-mark-or-move-to-trash is an interactive compiled Lisp function in
‘/usr/local/Cellar/mu/1.4.1/share/emacs/site-lisp/mu/mu4e/mu4e-headers.el’.

It is bound to d, .

(mu4e-headers-mark-or-move-to-trash)

Mark message for "move" to the trash folder if the message
maildir matches any regexp in ‘mu4e-move-to-trash-patterns’.
Otherwise mark with the "trash" flag.
Also see ‘mu4e-view-mark-or-move-to-trash’.

The variable mu4e-move-to-trash-patterns is set to nil, and mu4e-view-mark-or-move-to-trash shows:

mu4e-view-mark-or-move-to-trash is an interactive compiled Lisp function in
‘/usr/local/Cellar/mu/1.4.1/share/emacs/site-lisp/mu/mu4e/mu4e-view.el’.

(mu4e-view-mark-or-move-to-trash &optional N)

See ‘mu4e-headers-mark-or-move-to-trash’.

How can I send each message to the trash of its own mailbox?

Answer 1

The answer was in that same tutorial with the use of contexts:

(setq mu4e-contexts
 `( ,(make-mu4e-context
     :name "Gmail"
     :match-func (lambda (msg) (when msg
       (string-prefix-p "/Gmail" (mu4e-message-field msg :maildir))))
     :vars '(
       (mu4e-trash-folder . "/Gmail/[Gmail].Trash")
       (mu4e-refile-folder . "/Gmail/[Gmail].Archive")
       ))
   ,(make-mu4e-context
     :name "Exchange"
     :match-func (lambda (msg) (when msg
       (string-prefix-p "/Exchange" (mu4e-message-field msg :maildir))))
     :vars '(
       (mu4e-trash-folder . "/Exchange/Deleted Items")
       (mu4e-refile-folder . exchange-mu4e-refile-folder)
       ))
   ))