Sending from a new domain: how to get the first thousand emails delivered

The first sends from a new domain are a test you cannot retake cheaply. Gmail, Microsoft and the rest build a picture of a sender from behaviour, and the picture formed in the first two weeks is the one they carry forward. Fix it later and you are arguing with a filter that already made up its mind.

None of this is difficult. It is just ordered, and most shops do it in the wrong order — biggest list first, authentication afterwards.

Before the first send: authenticate all three

SPF, DKIM and DMARC are not optional any more. Google and Yahoo both require authentication for bulk senders, and a domain without DMARC is a domain whose mail can be spoofed and will be treated with suspicion.

1. SPF — one record, listing the services allowed to send as you. Watch the ten-lookup limit; it is the most common silent failure.
2. DKIM — signing keys published in DNS. Use a selector per sending service so you can rotate one without breaking the others.
3. DMARC — start at p=none with an rua address, read the reports for a fortnight, then move to quarantine and reject.

Send a test to a mailbox at each major provider and read the raw headers. "Pass" on all three, or do not proceed.

The first audience is the smallest one

Do not start with the list. Start with the people most likely to open, click and reply: customers who bought in the last thirty days, and anybody who subscribed this month.

• 500–1,000 addresses is a good first day.
• Exclude anybody who has not engaged in six months entirely, for the first month. They can come back once the domain has a history.
• Exclude role addresses — info@, sales@, support@. They rarely open and sometimes complain.

The ramp, roughly

Double every two or three days, watching the numbers rather than the calendar. A workable shape for a shop with a 20,000-address list:

1. Days 1–3: 1,000 a day, most engaged first.
2. Days 4–7: 2,500 a day.
3. Week 2: 5,000, then 10,000.
4. Week 3: full volume, if and only if the signals below are clean.

If complaints or bounces rise, hold at the current volume rather than pushing on. A ramp that pauses for three days costs nothing. A domain that gets filtered costs months.

The three numbers that decide it

• Spam complaints. Google enforces above 0.3 % and recommends staying under 0.1 %. At 1,000 sends that is one complaint. Two is a pattern.
• Hard bounces. Over 2 % says your list is older or dirtier than you thought. Stop, verify, restart.
• Engagement. Clicks and replies, not opens — opens have been unreliable since Apple's Mail Privacy Protection. A first send to your best customers should click well above your eventual average. If it does not, the problem is the content, and sending more of it is not the fix.

Keep receipts on a different subdomain

Order confirmations and marketing should never share a sending domain. They have different complaint profiles, different engagement, and a marketing campaign that goes wrong should never be able to stop a receipt reaching a customer.

Two subdomains under the same root — one for transactional, one for campaigns — with separate DKIM selectors and one DMARC policy at the root. Warm them separately. The transactional one warms itself, because people open receipts.