start_warmup
Begin the gradual warmup ramp on a mailbox, moving it from pending to warming.
›Start gradual warmup on every mailbox that is still pending.
What it does
Moves a mailbox from `pending` into `warming` and puts it on the schedule that raises its daily allowance over time. A warmup schedule maps day ranges to daily limits, so early days stay deliberately small and the ceiling lifts as history accumulates.
Mailboxes graduate `pending` → `warming` → `ready`. Only a ready mailbox is fully eligible for campaign volume, and the progression is driven by the hourly pipeline rather than by you remembering to raise a number.
This is the default choice for any newly created address. The ramp is the cheapest deliverability insurance available.
Starting warmup on several mailboxes at once is fine and usually correct, since capacity comes from breadth rather than from pushing any single address harder. What matters is that a pool account exists first — a ramp with nowhere to send is just a status change.
Parameters
| Name | Type | Notes |
|---|---|---|
| mailbox_id * | string | From `list_mailboxes`. |
* required · Maps to POST /api/warmup/start
What comes back
The updated mailbox with warmup stage `warming`.
The thing people get wrong
Starting warmup does not mean you should also start a campaign from that mailbox the same day. Let the ramp do its work before you enroll leads on it.
Use it with
More warmup tools
See all 22 tools and the connection string on the MCP server page.