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Troubleshooting Sender Authentication

My DNS records aren't validating

After you add your CNAME, TXT or MX records to your DNS host, you need to validate them in the SendGrid UI. If your DNS records aren't validating, try the following steps.

Allow your DNS records to propagate

Some DNS providers take longer than others to update your DNS records with the CNAME files or TXT and MX files that we ask you to add. Give it up to 48 hours to validate.

Auto appending

Some DNS hosts will automatically add your top-level domain to the end of DNS records you create, which can turn a CNAME for “email.domain.com” into “email.domain.com.domain.com”.

Be sure to follow the convention on existing records in your DNS panel when adding new ones, as sometimes you will only need to add what is to the left of the top-level domain.

For example, a CNAME for “email.” becomes “email.domain.com”

Error validating domain: Expected TXT record at...

Error validating domain:
Expected TXT record at "m1._domainkey.example.com" to match "k=rsa; t=s; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDHLyl8Wk4J06nv56v5+OeEgp9LW3f/""LOlBjWJ9NS4l9X5UlbPJkKeHDXThTig2CxhVuKmIVvRcc9yJ27Tdthj1C1q0rvRtFpNlHbdrJvD8wpxe5rmFeiRPH1KUYbvtbs84aApMwN6Y3A0dgQE7vGkHnPTjwT7q/xv3mu2CvkVntQIDAQAB", but got the following error: lookup m1._domainkey.example.com: no such host

If you get an error like this, the problem is that the TXT record has been split up. The solution is to combine the key back together into one set of quotes, which looks something like this:

"k=rsa; t=s; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDHLyl8Wk4J06nv56v5+OeEgp9LW3f/LOlBjWJ9NS4l9X5UlbPJkKeHDXThTig2CxhVuKmIVvRcc9yJ27Tdthj1C1q0rvRtFpNlHbdrJvD8wpxe5rmFeiRPH1KUYbvtbs84aApMwN6Y3A0dgQE7vGkHnPTjwT7q/xv3mu2CvkVntQIDAQAB"

DNS record duplication

Some DNS providers don't automatically prevent you from duplicating a DNS file. For example, there might be an MX and TXT record where you are trying to set up a CNAME file. If your DNS files aren't validating, check to make sure there are no other DNS records that could be a duplication.

My DNS doesn't accept underscores

SendGrid requires underscores for sender authentication, but some DNS providers do not support underscores in zone file entries.

If your provider does not allow you to use underscores in zone files, consider changing your DNS hosting provider.

Though you can disable automated security — this allows you to set TXT and MX records rather than CNAME records — a DKIM record will always contain an underscore.

DKIM record using a CNAME record


DKIM record using a TXT record


For more information about setting up automated security, see Using automated security.

Manually validating records

Sometimes there is no other option but to manually validate your DNS records. This can be caused by certain DNS providers or by customizations you add to your records.

To validate a DNS record manually, use the Unix command DIG. The following examples use Terminal on a Mac platform. The tables show specific validations. If the ANSWER section of the dig return is empty, that usually means that either the record does not exist or has yet to propagate.

Automated Security ON

Command Type ANSWER
dig cname sub.domain.com CNAME u123456.wl.sendgrid.net
dig cname s1._domainkey.sub.domain.com CNAME s1.domainkey.u123456.wl.sendgrid.net
dig cname s2._domainkey.domain.com CNAME s2.domainkey.u123456.wl.sendgrid.net

Automated Security OFF

Command Type ANSWER
dig mx sub.domain.com MX mx.sendgrid.net
dig txt m1._domainkey.sub.domain.com TXT k=rsa; t=s; p=MIGfMA0GC...
dig txt sub.domainkey.domain.com TXT v=spf1 include:sendgrid.net ~all

Email Links

Command Type ANSWER
dig cname links.domain.com CNAME sendgrid.net
dig cname 123456.domain.com CNAME sendgrid.net


Command Type ANSWER
dig a o1.default.domain.com A (your SendGrid IP address)

You can also use the DNSLookup tool provided by MxToolbox.

If you can successfully verify your DNS changes manually, but it won't validate in the tool, contact Support, and we can help you investigate.

Where is my domain hosted?

If you aren't sure what DNS provider hosts your domain use this command to find out:

dig <<your_domain.com>> ns

Can I authenticate multiple domains?

Yes, it’s possible to authenticate multiple domains. When multiple authenticated domains exist on your account, SendGrid will use the from address for each email you send through SendGrid and match it to a domain and branded link. If the from address does not match an existing authenticated domain, SendGrid will fall back to the domain you have chosen as the default.

Domain authentication application logic

Run through your application logic to understand why your sent emails may not be using sendgrid.net instead of the domain you authenticated.

If SendGrid cannot match your email to a valid authenticated domain, sendgrid.net is used.

For any account, SendGrid attaches authenticated domain information in the following order, starting at the top of the list and applying the domain when the criteria are matched:

  1. Valid authenticated domain that matches the domain in the FROM address.
  2. Valid default authenticated domain.

If no valid authenticated domains can be found, your mail domain defaults to sendgrid.net.

For subusers, SendGrid attaches authenticated domain information in the following order, starting at the top of the list and applying the domain when the criteria are matched:

  1. Authenticated domain for this subuser that matches the domain in the FROM address.
  2. Default authenticated domain for this subuser.
  3. Authenticated domain assigned by the parent account to this subuser.

If no valid authenticated domains can be found, the sending domain defaults to sendgrid.net.

Additional resources

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Need some help?

We all do sometimes; code is hard. Get help now from our support team, or lean on the wisdom of the crowd browsing the SendGrid tag on Stack Overflow.


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