Two ways to get mailboxes
Mailboxes live under Connections ▸ Emails.
Email accounts done-for-you is the recommended path. Click Get email accounts done-for-you, pick new domains (or add mailboxes to a domain you already have with Boostie), and name the mailboxes — up to 3 per domain. Get estimate shows the itemized cost and charges nothing; the order is placed only when you click Confirm & order. Setup takes one to three days, and the new mailboxes appear on the page when they are ready. Prices are on the pricing page.
Done-for-you mailboxes always sit on separate domains, never your main company domain, so your outreach sending stays apart from your everyday email.
Your own mailbox is the alternative, best if you already have warmed-up mailboxes. Click Add email account, fill in the address and sender name, then open it and use Connect this mailbox with a Google app password. Boostie checks the password with a real sign-in before saving it. For a domain Boostie doesn't manage, its DNS health stays your responsibility.
Every mailbox can carry its own HTML signature and a Sender matching group, which sends leads that match the group from that mailbox.
Why warmup exists
A brand-new mailbox has no sending history, and mail providers are wary of an address that goes from silent to busy overnight. Warmup builds that history gradually: the mailbox starts small and sends a little more each day.
A done-for-you mailbox warms for about two weeks after your order is confirmed; the order screen shows the date it should be ready. The Warmup column on the Emails page shows how each mailbox is doing. Mailboxes you connect yourself are not held back by Boostie's warmup.
You can start while mailboxes warm
You don't have to wait. Click Start campaign whenever your campaign is ready: a campaign whose mailboxes are still warming holds, shows the date it expects to start sending, and begins as soon as one of its mailboxes is ready. The only mailbox reason Start is blocked is having no connected mailbox at all.
More mailboxes, more volume
Each mailbox sends at most 30 emails a day. Boostie plans on 27 a day, leaving headroom for bounces and for mailboxes shared between campaigns, across 22 sending days a month on a Monday-to-Friday schedule.
So your monthly volume is set by how many mailboxes you have. Every step in your sequence is another email to each lead, so a longer sequence needs more mailboxes for the same number of leads. When you tell the AI your monthly volume, it works out how many mailboxes that takes and suggests the domains for them.
The full numbers behind this are on the deliverability page.