All ESPs
Transactional
SendGrid
SendGrid is one of the most widely deployed transactional ESPs. It supports SMTP and an HTTP API, with separate IP pools for transactional and marketing traffic. Authentication uses domain authentication with two CNAMEs per signing domain (s1._domainkey, s2._domainkey).
DNS records to publish
| Type | Host | Value |
|---|---|---|
| CNAME | em<id> | u<id>.wl<region>.sendgrid.netLink branding (tracking domain) |
| CNAME | s1._domainkey | s1.domainkey.u<id>.wl<region>.sendgrid.netDKIM key 1 |
| CNAME | s2._domainkey | s2.domainkey.u<id>.wl<region>.sendgrid.netDKIM key 2 |
Authentication setup
SPF
Add include:sendgrid.net to your SPF record (only required if you also use Sender Authentication's SPF mode — domain authentication uses CNAME-based DKIM by default).
DKIM
Publish the two CNAME records (s1, s2) shown in Sender Authentication. SendGrid rotates keys automatically.
DMARC
Start at p=none with rua reporting; once DKIM and SPF align consistently, ramp to p=quarantine then p=reject.
Deliverability tips
- Use a dedicated IP pool only above ~50k messages/month to a single mailbox provider; below that, shared pools usually outperform a new dedicated IP.
- Separate transactional and marketing onto different subdomains and IP pools to protect transactional reputation.
- Warm dedicated IPs gradually: 50, 100, 500, 1k, 5k, 10k per day per provider over 2-3 weeks.