Custom domain name versus Mailserver Domain


There are two types of domains you might set up to white-label your account: Custom Domain Name and 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 plans.

  • 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

Mailserver Domain

Available on all Marketing plans.

  • It is the actual name of the server that is sending your email. This domain is visible in the "mailed-by" you see in Gmail:
    Mailserver Domain in the 'mailed-by' in Gmail.png
  • This domain is checked for SPF and provides domain alignment for the SPF domain
  • When you set up authentication with ActiveCampaign, you set up a CNAME for a Mailserver Domain. Doing so points your domain to us so that we can use your domain as the Return Path domain, passing SPF. Setting up a Mailserver Domain is part of adding a sending domain in ActiveCampaign 
    Mailserver Domain in ActiveCampaign DNS records.png
  • 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

Why would I want to do this?

  • Both Custom Domain Names and Mailserver Domains allow you to white-label the platform, letting you 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
  • 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 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 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.

Things to keep in mind

  • You can only have one domain alias per account, but you can have as many Mailserver Domains as you want. One to match with each sending domain
  • 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 Mailserver domain, we recommend adding it to your Google Postmaster Tools
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