How to connect a mailbox from Claude

More mailboxes is the whole game

Cold email is a volume problem before it is anything else. One inbox can only send so much in a day before its reputation starts to wobble, so the teams sending real numbers do not lean on one account. They spread the load across many, each sending a modest, human amount. That pool is your sending infrastructure, and adding to it is the single most useful thing you can do.

The catch has always been the faff. Connecting a mailbox means digging out IMAP and SMTP hosts, app passwords and port settings, then repeating it for every account. Do that thirty times and you see why people put it off. Running it from Claude turns the whole chore into a sentence, and the batch of five you were dreading connects in one call.

What connecting actually does

When you ask Claude to add a mailbox it runs mailboxes_connect_imap_create, the same endpoint the app hits when you click through the setup screen. It checks the account can send and receive, then reports back. Nothing is hidden. You can ask to see the full list at any point and Claude will tell you which mailboxes are live and which failed, and why.

The bit that matters comes next, and it happens without you. A new mailbox starts warming straight away, on a real Google or Microsoft inbox rather than a bot or a raw SMTP relay, because warmup only means anything when the reputation it builds is real. Attach the mailbox to a campaign and rotation folds it into the pool automatically, so the sending spreads and no single account carries too much.

Adding capacity, not accounts

Think of each mailbox as a slice of daily headroom. Six inboxes on one domain, each sending a sensible amount, add up to far more than one inbox flogged to its limit, and they spread the risk while they do it. This is how a HotHawk workspace sends 40,000 emails a day and beyond: dozens of warmed inboxes each carrying a modest share, not one account carrying the lot.

So when a campaign needs more room, you do not rebuild anything. You add mailboxes. From the same chat you can check which ones are healthy, attach a fresh pool to a campaign, or spin up the campaign itself, each one a sentence away.