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This page assumes you know what SPF, DKIM and warm-up are. It covers what’s different on OpenMail: the cold cap does the warm-up, and reputation is tracked per inbox and per domain.

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Domain

1

Add a custom domain

Reputation built on the shared omail.sh isn’t yours. Add a custom domain (Pro and above) and run outreach from there.
2

Publish DMARC too

The domain verifies without it, so it’s easy to skip. Gmail and Yahoo require it from bulk senders. Keep an existing _dmarc record if you have one.
3

Probe before you write to anyone

Send between two inboxes on the new domain. It doesn’t count against the cold cap, and a bounce here means a DNS problem.
Keep cold mail on its own subdomain, like outreach.yourcompany.com, so a reputation hit never touches the domain your team uses. Several products or clients: one domain each. Each domain ramps on its own, but the account cap still applies, so this buys isolation, not volume.

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Sending

Warm-up is built in. A new domain ramps as it ages and as you actually reach people; there’s no schedule to follow and no need to hit the cap every day. Three things that slow it down:
  • Adding inboxes for volume. Caps are per domain and per account, so 50 inboxes on a new domain still share 20 new recipients a day. Create inboxes for separate identities, not throughput.
  • Bursting. 10 a minute per inbox is the hard limit, but a domain that sends 50 at 09:00 and nothing until tomorrow looks like a blast. Queue cold sends over the working day.
  • Retrying a 429. The response names the cap and resetsAt (midnight UTC). Another inbox on the same domain hits the same cap. See When you get a 429.
Over 5% bounces in a week throttles the inbox; 10% suspends it, and only a review lifts that. Validate addresses; don’t buy lists.

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The first message

Filters read the first message to a stranger more harshly than anything after it, and a reply is what grows your cap. Write to earn one.

Do

  • Open with their name and something specific to them
  • Ask one question; leave the pitch for the reply
  • Keep it short enough to read on a phone without scrolling
  • Send the link once they’ve answered

Don't

  • Open with a sentence that could have gone to anyone
  • Use “free”, “limited time”, capitals or exclamation marks
  • Put links or images in the first message
  • Add a tracking pixel — it’s an image, and trips the same filters
Plain text is handled: the API generates a text part for every HTML message and adds no tracking pixel.

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Bounces and complaints

An address that bounces, complains or unsubscribes goes on your suppression list and later sends to it return 422 recipient_suppressed. When your agent sees that, drop the contact or try another channel. Don’t look for a way around it; a second bounce to the same address is what costs reputation.

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What’s next

Rate limits

The exact caps per plan and the reputation thresholds.

Custom domains

DNS records, verification and pod scoping.

Suppressions

The three reasons an address is refused, and the error you get.

Idempotency

Safe retries so a 429 never turns into a duplicate send.