How to unify IMAP folders between different mail clients and automatically create them?

Warning: This workaround is not officially supported. All changes, committed to the configuration might be overwritten by future Plesk updates, upgrades, or repairs.

Modify IMAP server configuration to enable SPECIAL-USE RFC 6154 tags:

1. Connect to the server via SSH

2. Create and open /etc/dovecot/conf.d/30-plesk-specialuse.conf file using a text editor:

   # vi /etc/dovecot/conf.d/30-plesk-specialuse.conf

3. Add the namespace inbox block to include mailboxes (folders) with special_use tags:

   namespace inbox {
   separator = . 
   prefix = INBOX. 
   inbox = yes 
   mailbox Sent { 
   auto = subscribe 
   special_use = \Sent 
   } 
   mailbox "Sent Messages" { 
   auto = no 
   special_use = \Sent 
   } 
   mailbox Spam { 
   auto = create 
   special_use = \Junk 
   } 
   }

   Here, folder Sent Messages will be aliased to the folder Sent, and folders Sent and Spam will be created automatically.

   Note: This feature is available in Dovecot 2.1 and newer and is not provided by Courier-IMAP.
   For more detailed information refer to the official Dovecot Wiki.

4. If Plesk Email Security is installed, create the file /etc/dovecot/conf.d/custom_sieve/move_spam.sieve with the following content:

   require ["fileinto","mailbox"];
   if allof (header :contains "X-SPAM-Flag" "Yes")
   {
   fileinto :create "Spam";
   stop;
   }

5. Create the file /etc/dovecot/conf.d/99-move_spam.conf with the following content

   plugin { 
   sieve_after = /etc/dovecot/conf.d/custom_sieve/move_spam.sieve 
   }

6. Reload Dovecot IMAP server to apply new configuration:

   # service dovecot reload

Note: Newly created folders will not replace the specific existing ones made via the mail client by default like Sent folder for example.