Custom Domain versus Custom Mail Server Domain

There are two types of domains you might setup in order to white-label your account: Custom Domain and Custom Mail Server Domain. Here is a quick rundown of the differences between these two domains so you can know how these affect your campaigns:

Custom Domain

  • Available on Plus plans and up.
  • It is a unique URL primarily used for branding purposes. Changing this will give you a private/white-labeled login URL for your account.
  • This is set up by creating a CNAME record at any of your subdomains that points to your account url ( This is found under the My Settings  Domains page (image below) and we have a doc to help with the setup here.
  • Once set up, your campaigns and automation emails will use a custom link tracking domain instead of using the default shared link tracking domain.

Custom Mailserver Domain

  • Available only to Enterprise plans
  • It 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. Here is an example:
  • This is set up by submitting a ticket to We will then provide instructions for setting up the appropriate CNAME record.
  • When complete, you will see a different “mailed-by/sent on behalf of/sent via” field:
  • This will not change your ActiveCampaign account URL or tracking links, unlike setting up a custom domain.

Why would I want to do this?

Above all, both of these allow you to white-label the platform, going so far as to mask the mail server with your own domain.

In addition, domain-based reputation is on the rise. This means that Inbox Providers like Gmail are watching very closely for the type of activity associated with a particular domain. If they see that email using a domain is often marked as spam by Gmail users, that domain will acquire a negative reputation.

By default, you use ActiveCampaign's shared domains. This means you also inherit these shared domains' reputations. This is not a bad thing, because we work very hard to ensure these domains are only used by users with very clean, opt-in lists.

However, some users may want to take deliverability entirely into their own hands so that they have 100% control over their sender reputation. Setting up these domains both have essentially the same effect on deliverability: they give you further independence from the shared ActiveCampaign reputation. However, this is not guaranteed to help deliverability, and doing so should not be thought of as a band-aid for more serious deliverability issues.

Things to keep in mind:

  • You can set up both. But you can only set up one of each. So you can't have 2 Domain Aliases, for example.
  • The same domain can't be used for both. If you choose to setup both at the same root domain, each must be unique subdomains. For example: (Domain Alias) (Mail Server Domain)
  • Neither of these will remove the “via”/”on behalf of” header. To hide this, see here.
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