Sending limits that protect your domain.

Seven things every mailbox runs under.

Each one is something the system does or refuses to do. None is a promise about where your mail lands, because that depends on your content and your recipients as much as on our infrastructure.

1. 01

   Mailbox warm-up

   A newly connected mailbox starts at 5 sends a day and adds 2 a day until it reaches its daily cap. The ramp follows the calendar, so a busy week can't skip it.

   What it refuses
   While a mailbox is ramping it won't send past that day's cap, however many approved drafts are waiting.

2. 02

   Paid address verification

   Every address goes to a paid verification service, which asks the recipient's mail server rather than checking the spelling. It comes back valid, risky, invalid or unknown. Addresses are checked when the account is researched, and any address still without a result is checked when its draft is written.

   What it refuses
   An address confirmed invalid is never emailed. A risky one, usually at a domain that accepts all mail, only sends while your bounce rate is healthy. One the service couldn't answer for is held and re-checked, and dropped if it's still unconfirmed a day later. How we found the address makes no difference; the result decides.

3. 03

   A daily ceiling

   Each mailbox sends up to 20 cold emails a day by default. You can raise that to the platform ceiling of 50, and no higher; hourly, weekly and monthly ceilings apply too. A mailbox on a free provider such as gmail.com is held to 10 a day. Sends are spread through the day, and quiet hours follow the recipient's timezone, not yours.

   What it refuses
   Cold outreach can't go past the ceiling. Your own reply to someone who wrote to you is the one thing it doesn't hold back.

4. 04

   Tiered bounce brakes

   Each mailbox's bounce rate is measured over the last 30 days, once it has at least 10 sends. At 3% you get a warning, and only addresses confirmed valid are sent to. At 4% daily volume also drops to 5, then climbs by 2 a day to at most 10. At 7% the mailbox stops sending cold email.

   What it refuses
   Each brake releases below the rate that tripped it: the warning under 2%, the lockout under 3%, the halt under 5.5%. Without that gap, a rate hovering near a line would switch sending on and off all day.

5. 05

   A way back from a halt

   A halted mailbox sends nothing, so its bounce rate can't improve. It can only wait for old sends to leave the 30-day window. Recovery mode lets it send a small daily allowance, starting at 5, to the safest recipients it has: people who have replied before, then addresses confirmed valid. Those sends count, so a clean run shortens the halt.

   What it refuses
   Each step up is earned by clean sends, never by time passing.

6. 06

   Domain and DMARC checks

   We read your sending domain's SPF, DKIM and DMARC records and show you what we find. If you point your DMARC reports at a Gmail or Microsoft mailbox you've connected, we read those too and show how your mail is authenticating, domain by domain.

   What it refuses
   A DNS lookup that doesn't answer is shown as unknown, never as missing. Reports that stop arriving are shown as stale, not as healthy.

7. 07

   Opt-outs that stay out

   Unsubscribe links are signed, so nobody can forge one or guess someone else's. An opt-out stops automated outreach to that address from every mailbox in your workspace, and it still applies if the company is found again later.

   What it refuses
   A message that can't carry your sender details and a working unsubscribe link doesn't send at all.

Do I send from my own domain?

Yes. You send from a mailbox you connect: Google, Microsoft or your own SMTP server. The domain is whichever one that mailbox is on, so to send from a separate domain you connect a mailbox on it. We don't own, share or provision sending domains, so the reputation you build stays on infrastructure you control.

Can you guarantee my mail lands in the inbox?

No, and no vendor can. Where mail lands depends on your content, your recipients and your domain's history as much as on how carefully it's sent. What we can tell you is what the system enforces: the ceilings, the verification, the brakes, and the rule that a message without your sender details and an unsubscribe link doesn't send. If a vendor promises inbox placement, ask what happens when it doesn't arrive.

What happens if my bounce rate climbs anyway?

Sending tightens in steps. At 3% you get a warning and only confirmed-valid addresses are sent to. At 4% daily volume drops to 5 and climbs back slowly. At 7% the mailbox halts. A halt has no fixed length, and cleaning your list won't lift it, because the rate covers the last 30 days of sends. It lifts as old sends age out, and recovery mode can shorten it.

Why not check each address right before it sends?

Because a call to an outside service inside the send loop would make your sending depend on that service being up. Addresses are checked when the account is researched, and any address still without a result is checked when its draft is written. A result is trusted for up to 90 days before it's checked again. At send time the system uses the result it already holds, and an address that is still unconfirmed is held back.

Related reading: cold email deliverability and sender reputation in the glossary, and how consent and opt-out are handled.