All ESPs
Newsletter
Substack
Substack handles its own sending infrastructure; writers cannot publish their own DKIM, but a CNAME-based custom domain is supported.
DNS records to publish
| Type | Host | Value |
|---|---|---|
| CNAME | <custom> | <id>.substack.comCustom domain (optional) |
Authentication setup
SPF
Not customer-configurable. Substack uses its own sending domain (substack.com).
DKIM
Not customer-configurable. Substack signs with its own keys.
DMARC
Substack publishes its own DMARC at substack.com.
Deliverability tips
- If you also send transactional mail from your domain, Substack does not affect your domain's reputation directly because their From: header uses substack.com.
- Use a custom domain only for the web reader experience — the sending domain remains substack.com.
- Avoid 'forward this email' style content; Substack's reputation suffers from forwarded chain mail at Gmail.