Email deliverability fundamentals
Understand acceptance, inbox placement, authentication and recipient expectations before investigating a problem.
A useful investigation starts with a precise question. “Our emails are not working” could mean a sending failure, a rejection, spam placement or simply fewer people responding. Each needs different evidence.
Separate the stages
| Stage | Evidence to collect | What remains unknown |
|---|---|---|
| Submitted to your ESP | Campaign or message ID | Whether the destination accepted it |
| Accepted by the receiving server | Final SMTP response | Which folder received it |
| Observed in a mailbox | Folder and full headers | Placement for other recipients |
| Recipient acted | A reply, click or relevant conversion | Why other recipients did not act |
Learn the three authentication names
SPF checks whether a sending server is authorized for the envelope domain. DKIM verifies a domain's signature over signed message content. DMARC connects an authenticated identity to the visible From domain through alignment. A passing authentication result does not promise inbox placement.
Include the audience in the investigation
Write down what the subscriber signed up for, how often you said you would send and what changed recently. A technically correct setup can still deliver an unexpected message to an uninterested audience. Review the subscription and the sending configuration together.
Build a small evidence record
Keep the first observed date, message type, destination provider, sending system, complete response and a representative message. Compare like with like: the same stream and provider over comparable periods. Keep an observation separate from your explanation of it.
Record the observed result separately from the suspected cause. Do not present an explanation as established until the evidence supports it.