A shared mailbox (support@, legal@) belongs to no one person: nobody
signs in to it, and the people assigned open it beside their own mail
at an access level an administrator chose. An account lock already is
most of that: it keeps receiving mail, refuses every sign-in, and its
delegates reach it through real grants on every container (so IMAP,
DAV and JMAP honor them), never including Share. So a shared mailbox is
a lock of a second kind (multi-account spec, MA-S; John, 2026-10-05).
Lock gains kind: "lock" (the default, so stored locks read as before)
or "sharedMailbox", set on create and fixed after. A shared mailbox:
- needs no reason to make, change or end;
- holds up to 100 people, where a lock holds 10;
- runs its own Sieve replies and redirects, so an automatic
acknowledgement goes out (a lock answers no one);
- records only what is sent as it (audit_send_as, which now covers it),
not AL-9's access and per-change records, which would bury the log
for a busy desk;
- sends only as itself (MA-S3): From and Reply-To must be its own
addresses, so answers come back to the mailbox and not to whoever
replied; anything else is forbiddenFrom.
The session marks it delegation: {locked: true, kind: "sharedMailbox"},
so a front end that knows no kind still treats it as a lock. The
console's layout gains Management › Directory › Shared Mailboxes
(CustomComponent/SharedMailboxes).
Tests: the account lock suite now goes on to a shared mailbox: made
without a reason with twelve people, sign-in refused, the session's
kind, its vacation reply delivered, an answer sent as it and recorded
as the agent with no per-change records, and a Reply-To naming the
agent refused; a lock unit test reads a stored lock without a kind.
account_lock_tests, jmap_tests, audit_log_tests and imap_tests pass
(RocksDB).
A locked account can't sign in (it fails as a wrong password does), its
sessions end on every node, refresh tokens stop working, and its Sieve
scripts forward and reply to nothing. Mail keeps arriving.
Delegates get real ACL grants on the account's mailboxes, calendars,
address books and files at read, organize or full, with the rights they
replaced restored on unlock. Folders made later are granted after the
create and in a daily sweep. Organize delegates can't destroy; send-as
needs organize or full. The JMAP session marks delegated accounts in
urn:inbuxa:jmap.
New inbuxa:AccountLock object with get/set, permissions 665-668, and a
Compliance > Locked Accounts entry in the schema. Lock, unlock and
delegate changes need a reason and are audited; delegate access and
writes are audited too (audit-hold-lock spec AL-1 to AL-12).
jcoffey-dev