The mailbox is either inactive, soft-deleted, or is hosted on-premise
This message shows up in 2 different situations. Pick the one that matches yours:
- A mail-permission probe that can't tell "no mailbox" from "no consent" lies to admins/me/messages 404 MailboxNotEnabled* on mailbox-less accounts ≠ missing consent; three verdicts, and never cache a negative probe resultCause and fix →
- A mailto: fallback that reuses the success state tells the user their message was sent when it wasn'tsendMail fails on accounts without a mailbox and the fallback only hands a draft to a mail client; model sent / handed off / failed, never a booleanCause and fix →