A cold email deliverability checklist should establish whether the sender is correctly configured, the audience is appropriate and the team can respond to delivery problems. Passing DNS checks does not guarantee inbox placement, and a warmup score does not prove that real recipients want the campaign.

Use this checklist before a new campaign and when delivery deteriorates. Record evidence from the actual sending path rather than relying only on a setup dashboard. Provider requirements checked 11 September 2026; review the linked primary guidance when making changes.

1. Identify every system sending as your domain

List the mailbox provider, sequencer, CRM, marketing platform and any other service sending mail. Record the visible From address, return-path domain, DKIM signing domain and responsible owner. This helps distinguish a campaign problem from a different service affecting the same domain.

Send an internal test through the same path the campaign uses. Inspect the received message headers. A message sent directly from the mailbox interface may take a different path from one sent through another service.

2. Check authentication and alignment

Do not publish a generic SPF record copied from another company’s guide. The correct configuration depends on your authorised services. Equally, moving directly to a strict DMARC policy without checking legitimate senders can interrupt other mail. Collect the evidence and involve the domain administrator where changes are required.

3. Apply the destination provider’s requirements

For personal Gmail recipients, Google requires SPF or DKIM for all senders, with additional requirements for bulk senders around 5,000 messages a day: SPF, DKIM, DMARC alignment and one-click unsubscribe for marketing or subscribed messages. Google requires spam rates below 0.3% and recommends staying below 0.1%. Google sender guidelines.

Yahoo requires SPF or DKIM for all senders and SPF, DKIM and DMARC for bulk senders. Its guidance requires spam complaints below 0.3%, appropriate unsubscribe support and requests honoured within two days. Yahoo describes bulk volume without publishing the same fixed threshold as Google. Yahoo sender requirements and FAQ.

Microsoft’s Outlook.com requirements apply stronger authentication rules to high-volume senders. Authentication failures can produce the 550 5.7.515 rejection. Check the exact error and current scope in Microsoft’s troubleshooting guidance.

These are provider requirements, not a complete legal checklist or permission to send unwanted mail. Lower volume does not exempt a sender from acceptable-use policies or recipient expectations.

4. Review the audience and exclusions

Confirm why the selected audience is appropriate for the message and what permission or other requirements apply to the campaign. Remove wrong-company records, stale roles and invalid addresses. Keep opt-outs and other exclusions available to every system that can initiate contact.

Run a suppression test before launch: add an internal test contact to the exclusion list and verify that no relevant campaign can send to it. Repeat after a migration or integration change. Contact verification does not establish consent, interest or suitability.

5. Test unsubscribe and reply handling

Where one-click unsubscribe is required, a sentence asking recipients to reply is not an equivalent implementation. Check the headers and the resulting suppression update. Also test the visible unsubscribe route and an ordinary negative reply.

Confirm that a positive reply stops scheduled follow-ups and reaches an owner. A sequence continuing after a conversation has started can be confusing and damage trust even when authentication passes.

6. Review identity and message accuracy

Check the sender name, subject, first line and links. They should accurately describe who is writing and why. Do not use a false reply prefix, invented referral or unsupported claim. Make the destination of links understandable.

Preview the message on a phone and in a plain-text view. Confirm that the essential context and opt-out route remain clear. The subject-line guide gives examples built around accurate observations.

7. Start from readiness, not a universal daily limit

There is no fixed number of daily emails or weeks of warmup that guarantees safe delivery across accounts. Follow the mailbox provider’s limits, begin with appropriate expected activity and monitor changes. Do not add accounts or domains simply to evade restrictions.

If delivery worsens, pause the affected activity and investigate the actual error, recipient segment and sending path. Keep the last known good configuration available so changes can be compared. An automated warmup network cannot substitute for that diagnosis.

8. Record the signals that change decisions

Seed tests can offer diagnostic evidence, but they are not a guarantee for every real recipient. Read email warmup tools before adding another service. If the team needs help owning setup and ongoing review, explore managed infrastructure or contact Rhycon with a redacted delivery error and your sending setup.