Custom domain name versus custom mailserver domain


There are two types of domains you might set up to white-label your account: Custom Domain Name and Custom Mailserver Domain. Here is a quick rundown of the differences between these two domains so you can know how these affect your campaigns.

Custom Domain Name

Available on Marketing Plus, Professional, and Enterprise.

  • It is a unique URL primarily used for branding purposes. Changing this will give you a private/white-labeled login URL for your account

    custom domain url.png
  • 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

    Domain alias page example.jpg
  • 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 on Marketing Enterprise.

  • 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:
    Sent on behalf of example.png
  • This is set up by submitting a ticket. 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?

  • Both Custom Domain Names and Custom Mailserver Domains allow you to white-label the platform, going so far as to mask the mailserver with your own domain
  • 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. All customers use ActiveCampaign's shared domains by default. 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. 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
  • Another common reason for setting up the Custom Mailserver Domain is to align your Return Path/Mail From/SPF domain with your own domain for DMARC. With ActiveCampaign, 100% of your messages will pass SPF with our mailserver domain by default, but this does not match the domain in your From Address. Setting up a Custom Mailserver Domain will allow you to align your SPF domain with your From Address domain for DMARC compliance. Read more about domain alignment
  • Aligning either the DKIM or Mailserver Domain is required for account that send over 5,000 emails a day as of February 2024 following upcoming changes to Gmail and Yahoo regarding authentication requirements. ActiveCampaign highly reccommends all senders set up DKIM and DMARC. For more information on these changes see our blog post A Guide to Google and Yahoo authentication Changes in 2024.
    Setting up a Custom Mailserver Domain that matches the domain used in your From Address will fulfill these requirements. However, since you can only have one custom mailserver domain per account, it’s also recommended to set up DKIM for every domain you use with ActiveCampaign to be sure.

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 set up both at the same root domain, each must be unique subdomains. For example:
    • (Domain Alias)
    • (Mailserver Domain)
  • Neither of these will remove the “via”/”on behalf of” header. To learn how to hide this, visit How to remove the "Send on behalf of" header
  • Once you have a Custom Mailserver domain, we recommend adding it to your Google Postmaster Tools
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