# 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

```bash
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:

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

### My Sender Authentication Was Successful, but My DMARC Failed

Sender Authentication confirms the validity of SPF, DKIM, and DMARC records. However, a DMARC pass is not mandatory for successful Sender Authentication. You will be routed to the successful authentication page, and be able to send mail. The 'Install DNS Records' UI will indicate a DMARC failure, alerting you to address the issue with your DNS provider.

### 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**

```bash
s1._domainkey.example.com
```

**DKIM record using a TXT record**

```bash
m1._domainkey.example.com
```

For more information about setting up automated security, see [Using automated security](/docs/sendgrid/ui/account-and-settings/how-to-set-up-domain-authentication#use-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` |

### IPs

| Command                       | Type | ANSWER                                   |
| ----------------------------- | ---- | ---------------------------------------- |
| `dig a o1.default.domain.com` | A    | `12.34.56.78 (your SendGrid IP address)` |

You can also use the [DNSLookup](https://mxtoolbox.com/DNSLookup.aspx) tool provided by MxToolbox.

If you can successfully verify your DNS changes manually, but it won't validate in the tool, contact [Support](https://support.sendgrid.com/hc/en-us), 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:

```bash
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 be using `sendgrid.net` instead of the domain you authenticated.

> \[!NOTE]
>
> 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

* [How to set up domain authentication](/docs/sendgrid/ui/account-and-settings/how-to-set-up-domain-authentication/)
* [How to set up link branding](/docs/sendgrid/ui/account-and-settings/how-to-set-up-link-branding/)
* [How to set up reverse DNS](/docs/sendgrid/ui/account-and-settings/how-to-set-up-reverse-dns/)