It seems the imap connection to the 'delegated' account is done, as in sogod client i see '<0x0x96dcf121a10[NGImap4Client]> TLS started successfully.' messages - so maybe that's just a webui issue.

Oh and forgot to mention, using dovecot on OpenBSD, and a variety of subfolders in the Maildir space (ie some rooted under .INBOX.Foo, and others at the top like .Trash or .spam...)

And as a workaround, in b@tld account i can still configure a 'remote imap' account using a@tld account credentials (and using the public ip of the host, as 'localhost' gives a warning) - that works and lists a@tld folders in the view but that's awkward.

Configuring a@tld account as a remote imap account still triggers the same error message in the browser console:

Transition Rejection($id: 0 type: 2, message: The transition has been superseded by a different transition, detail: Transition#1( ''{} -> 'mail.account.mailbox'{"accountId":"0","mailboxId":"INBOX"} ))

but the folder list for both accounts is correctly displayed, and i see queries on <uid>/Mail/0/view and <uid>/Mail/1/view in the network console.

The doc doesnt mention if something has to be done in particular on the serverside, ie for dovecot should the specific accounts be configured as shared (and/or) public via namespaces ? (ie https://wiki.dovecot.org/SharedMailboxes/Public & https://wiki.dovecot.org/SharedMailboxes/Shared)

Delegation only allows you to send emails in the name of this other user.
You still have to share each folder this other user should see/use.

Isnt 'sending emails in the name of other user' a feature provided by using multiple identities ?

The SOGo documentation isnt totally clear about email delegation, so when you say 'you still have to share each folder this other user should see/use' it is at the imap server level (ie dovecot shared mailboxes) or within sogo, ie user a@tld has to 'explicitely share INBOX and subfolders' with b@tld in addition to enable delegation ? An example/usecase in the doc would greatly help.

Well, i tried 'sharing' INBOX in a@tld web view, giving all rights to b@tld account, but b@tld doesnt see any of the folders/subfolders from a@tld account - note that i havent configured any kind of sharing on the backend/dovecot side.

The only 'relevant' setting i see is 'DelegateFrom: "a" in the output of
sogo-tool user-preferences get settings b Mail - other than that i dont see where the ACLs are stored (not in the database?)

So, are we supposed to setup sharing in dovecot ?

Ok, after fighting a bit, i can confirm it for the next one who ends up on this issue - yes, you need to configure ACL/SharedMailboxes in your IMAP server - i have it working now with dovecot, and using 'plugin { acl_defaults_from_inbox = yes }' in its config, after sharing an inbox, i see all its folder subtree in the target account. Phew, wish the doc provided that full detailed setup..