How to set up your domain for sending emails

One of the ways spam filtering systems determine if an email is spam is to check the email header to see if the server sending the email is an authorized sender. This is done by checking the DNS for the email address of the person sending the email (the FROM email domain) and seeing if that domain has given permission to ContentMX to send email on its behalf. This is known as an SPF record.

In addition, the signature of the email header is checked against a key stored with the domain to confirm the email is authentic. This is known as a Domain Key (DKIM).

For instance, if you are sending an email from norton@mycompany.com, the spam filter will check the DNS records of mycompany.com to see if it authorizes email to be sent from the ContentMX email servers AND if the DKIM signature correlates to the domain key.

To configure your domain for sending email, you will need to add both an SPF record and a set of DKIM records to your DNS.

The Delivery Center walks you through this: it checks your domain, generates the DKIM records you need, and verifies your setup after the DNS changes are live. You (or your IT team) still make the DNS changes at your DNS provider.

Default sender: Set your default FROM address in My Profile under contact information, then save. That address should use the same domain you configure in the Delivery Center.

Using the Delivery Center

1. Log in to the platform and open My Profile.
2. Under your contact / email delivery status, click Set Sending Domain (or Verify Sending Domain / View/Change Sending Domain if you’ve already started).
3. In the Delivery Center, enter the email domain you will send from (for example, mycompany.com — not a full email address).
4. Click Check.

You’ll see an overall delivery score and the status of:

• SPF — whether the platform is authorized to send
• DKIM — whether the required domain keys are present and verified
• DMARC — whether a DMARC policy is published

Follow the on-screen guidance for any item that fails or needs attention. After DNS changes, return to the Delivery Center and click Check again (and Verify Domain for DKIM when prompted). DNS can take from a few minutes up to 24–48 hours to propagate. 

Adding the SPF record

To authorize ContentMX as a sender, you (or your IT administrator) should add ContentMX to the SPF setting in your DNS. This is done by adding or modifying the TXT record containing the SPF information. You will be adding “include:contentmx.net” to this record.

For example, if your SPF record looks like this:

you would modify it to look like this:

Once this change is made, it may take a little time for it to replicate across the Internet.

If you have no SPF record, the Delivery Center will suggest a starting value such as: v=spf1 include:contentmx.net -all

Important:

• Keep one SPF TXT record for the domain. Merge includes into that record; do not create a second SPF record.
• If you already send through Microsoft 365, Google Workspace, or another provider, keep those includes and add ContentMX’s.

The Delivery Center shows your current SPF and a suggested modification when ContentMX is missing. After you update DNS, click Check again to confirm.

Add your DKIM records

In the Delivery Center:

1. Enter your sending domain and click Check.
2. If DKIM is incomplete, click Register this Domain. ContentMX generates the DKIM CNAME records for that domain.
3. In the Delivery Center, copy the listed DNS records (typically three CNAME records).
4. In your DNS provider’s zone editor, add each record using the Record Type, Host/Name, and Value shown. Use the default TTL or 3600.
5. Wait for DNS propagation (often minutes to a few hours; sometimes up to 24–48 hours).
6. Return to the Delivery Center and click Verify Domain to confirm the records and finish registration.

TIP: Do not reuse sample records from the documentation — always use the exact Host and Value values shown for your domain in the Delivery Center. If verification fails, wait a bit longer for propagation, double-check each CNAME, then try to click the Verify Domain button again.

Add a DMARC record

DMARC tells receivers how to treat mail that fails SPF/DKIM and enables reporting. The Delivery Center checks for a DMARC record and guides you if one is missing. Email providers (like Google Gmail) are now requiring properly formed DMARC records to ensure email delivery.

Typical setup:

1. Add a TXT record with host _dmarc.
2. Use a policy value such as the one shown in the Delivery Center (you can start with monitoring and later tighten to quarantine/reject).
3. Save, wait for propagation, then click Check again.

If your organization already has a DMARC policy, keep it and confirm it works with your ContentMX setup rather than creating a conflicting second record.

After setup

When SPF, DKIM, and DMARC look good, your Delivery Center score should be 100% and will reflect that your domain is ready. Also confirm that the default email on My Profile uses the same sending domain.

You can reopen the Delivery Center anytime from My Profile to re-check or change the sending domain.

Need help?

If you can’t access DNS, or verification still fails after propagation, contact support@contentmx.com with your sending domain and a description of what you’re seeing in the Delivery Center. We cannot make the DNS changes for you, but we can guide you further on how to make the changes.