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    Chapter · DKIM for SendGrid
    Revised 17 Jun 2026
    Guide · DKIM · SendGrid

    How to set up DKIM for SendGrid.

    SendGrid (Twilio) is one of the most-used transactional ESPs. Their domain authentication wizard generates per-account CNAMEs you publish on a sending subdomain — never on your apex.

    Afsan Rahmatullah
    Afsan RahmatullahMailerMonk

    DKIM (DomainKeys Identified Mail, RFC 6376) is the cryptographic signature attached to outgoing email so receivers can verify the message wasn't tampered with and that it actually came from a server authorized by your domain. To turn it on for SendGrid, you publish one or more DNS records at `<selector>._domainkey.<your-domain>` containing the public key matching the private key SendGrid uses to sign.

    Most ESPs (including SendGrid) ask you to publish CNAME records that point at hosted keys they manage. This is preferable to publishing the raw key text yourself — when the provider rotates keys, your DNS keeps pointing to the rotated key and nothing breaks.

    Publish these DNS records

    Add the following record(s) to your domain's DNS zone. Most registrars (Cloudflare, Route 53, Namecheap, GoDaddy) accept values exactly as shown.

    Record · CNAME
    Type
    CNAME
    Host
    s1._domainkey
    Value
    s1.domainkey.u<NUM>.wl.sendgrid.net
    Record · CNAME
    Type
    CNAME
    Host
    s2._domainkey
    Value
    s2.domainkey.u<NUM>.wl.sendgrid.net
    Why this matters
    • Two selectors — `s1` and `s2`. Both are CNAMEs to SendGrid-hosted keys; SendGrid rotates between them, so omitting one will cause intermittent DKIM failures.
    • `<NUM>` is the same SendGrid-issued account number used in the SPF CNAME.

    Where in SendGrid

    The DKIM configuration lives in SendGrid → Settings → Sender Authentication → Authenticate Your Domain.

    Verify the records

    After the records propagate, run the DKIM Checker against your domain with each selector to confirm the public key resolves and parses correctly.

    From a terminal
    dig +short TXT <selector>._domainkey.your-domain.com
    Run the free DKIM checker

    Common pitfalls

    Pitfall
    • SendGrid's wizard sometimes fails to detect successful CNAME publication for several hours due to caching. If verification fails immediately, check `dig CNAME` from a different resolver before changing anything.
    • For shared IP plans, you have no control over IP-level reputation — DKIM signing on your domain is what protects deliverability.
    • SendGrid's free tier includes a `<random>.sendgrid.net` From: domain by default; only authenticated senders should ever use a real brand From: address.
    After you publish

    Want to know if it actually keeps working?

    MailerMonk continuously watches your DKIM record, aggregate DMARC reports, and inbox placement — and pings you the moment something drifts. Free for the first domain.

    Start free trial

    About the author

    Afsan Rahmatullah
    Afsan Rahmatullah
    MailerMonk

    Building tools that keep cold email out of spam. Writes about deliverability, DMARC, and what actually moves inbox placement.

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