Several accounts
Google and IMAP accounts can sit side by side. Add as many as you like: sign in with Google, or press ⌘ K and choose Add Account (see Set up Google and Proton Mail and other IMAP accounts). With more than one, the bottom of the narrow bar on the left holds All accounts and each account's picture.
One account at a time
Click an account's picture, or press ⌘ 1, ⌘ 2 and so on, to see that account's mail, splits and labels on their own.
All accounts
Press ⌘ ⇧ 0, or click the tray above the account pictures, to see every account's mail in one list, newest first. Kestrel stays on All accounts the next time you open it, until you pick a single account again.
- Each row starts with the picture of its account, and an open conversation names its account under the subject.
- Split Inbox tabs combine. Each account still sorts its own mail into its own splits; a tab gathers every account's split of that name. Important and Other are one tab each, and a split only one account has shows only that account's mail.
- Starred, Sent, Drafts, Done, Reminders, Scheduled, Spam and Trash show every account's mail.
- Search (/) looks through every account as you type, and Enter asks each account's server at once. An account that can't answer leaves the others' results.
- A label belongs to one account. The label menu lists the labels of the account you last switched to, and going to one shows that account on its own.
- Get Me To Zero clears old mail from every account.
- A conversation that reached two of your accounts (both on a mailing list, or copied to both addresses) shows once. The row is the copy with the newest message, or the copy in the account you last switched to.
Which account does what
Everything you do to a conversation happens in the account it belongs to: Mark Done, Remind Me, Star, Read, Mute, Trash, Spam, Move, labels, and undo. You can select conversations from several accounts and mark them done, set a reminder, star or trash them together. Label, Move and Remove Label use one account's labels, so they ask you to pick conversations from one account.
When one row stands for a conversation in two accounts, marking it done or not done, setting a reminder, starring, reading, muting, trashing or marking it as spam changes every account's copy, so it doesn't come back from the other account. Labels and replies use the account whose copy the row shows.
A reply or forward goes from the conversation's account, and its snippets are that account's. A new message (C) goes from the account you last switched to.
Each account keeps its own Split Inbox definitions and snippets. In All accounts, Split Inbox Settings edits the account you last switched to and says which one; switch to another account to edit its splits. Ask AI and Recent Opens also use the account you last switched to.
When an account can't sync
A bar above the list says why: Gmail asking Kestrel to slow down (it picks up again on its own), an expired Google sign-in (Sign in again), a password the server refused (Update password), or Proton Mail Bridge not running. In All accounts the bar names the account. The other accounts' mail stays in the list, and Retry tries only the account that failed.