How to set up a custom mailserver domain


Setting up a custom mailserver domain masks the ActiveCampaign email sending server with your domain. 

What is a custom mailserver domain?

A custom mailserver domain is the actual name of the server that is sending your email. By default, all emails sent from our platform will show the name of our email sending servers in the "sent on behalf of" or "sent via" email headers:


When you set up your custom mailserver domain, you will see a different "mailed-by", "sent on behalf", or "sent via" field.

If you want to completely remove "sent via" from your emails, follow the instructions in this "How do I remove the sent on behalf of header" help article.

Setting up a custom mailserver domain does not change your ActiveCampaign account URL or tracking links. For more information on this topic, please see the "Custom domain versus custom mailserver domain" help article.

How to set up a custom mailserver domain

Step 1: Set up a DNS custom domain (CNAME) record with your web host.

This record needs to point to the subdomain

For example, with GoDaddy, you must enter acmail as the Name and as the Value. Then leave TTL to the default value.

Do not edit any other DNS records when setting up the CNAME record.

Be careful not to replace or modify other CNAME records you may have set up like a CNAME for our Domain Alias feature.

Note that it can take a few minutes to 24 hours for the CNAME record to propagate publicly. You can use the Google Admin Toolbox to verify that the CNAME record for your subdomain is set up correctly.

You should see a result like this:


 Every domain host has a slightly different method of doing this. Here are instructions for common providers:

Step 2: When complete, contact our Customer Experience Team to let us know that you're requesting a custom mailserver domain and completed the step above. 

When we receive your message, we'll complete the rest of the custom mailserver domain setup on your behalf. 

Common questions

What is the difference between a custom mailserver domain and a domain alias?

A custom mailserver domain is a completely different feature than the Domain Alias even though both are set up via a CNAME record.

  • If you choose to use both features, you must use a completely different subdomain for each
  • These features are not dependent on one another, you can use one, both, or neither
  • You can only have one of each per account
  • Be sure not to edit the CNAME records that have already been set up or you can cause problems with your ActiveCampaign account that is using these domains
  • The domain that you use for a custom mailserver domain cannot be used for anything else, including another email service

Read the "Custom domain vs custom mailserver domain" help article for more information on this topic.

What subdomain should I use?

To set up a custom mailserver domain you will need to pick a subdomain of your domain to use exclusively as the custom mailserver domain. If you are also using the Domain Alias feature, you must use a completely different subdomain. We recommend using a subdomain of the same domain you are using in the From Address which helps with domain alignment.

For example, if you use as your From Address, you could use as the custom mailserver domain, so long as that domain is not used for anything else.

What if my CNAME is not set up correctly?

If you have modified your DNS records and the CNAME is no longer resolving correctly, you may see an error like this when you go to send a new campaign in ActiveCampaign:


To resolve this:

  1. Go to your DNS provider and re-add the CNAME record pointing to
  2. Wait 5-10 minutes and then refresh the Campaign Summary page. The error should be resolved.
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