Set Up Email Sending Domain (ActiveCampaign™)

Your main domain (yourbrand.com) is tied to your corporate email — every message your staff sends, and every reply from your customers, runs through it. Your main domain’s reputation is hard to build and easy to damage.

Email marketing operates on a different scale. Campaigns go to thousands of recipients at a time, and even a well-managed list will generate some spam complaints, unsubscribe requests, and bounces. Isolating that activity to a subdomain means those signals stay separate from your corporate brand’s email reputation.

If something goes wrong with a campaign, such as a deliverability issue or a spam complaint spike, it only affects the subdomain email.yourbrand.com. Since yourbrand.com is not affected, your team's day-to-day email is not put at risk.

For more information about subdomains, click here.

DKIM (DomainKeys Identified Mail) is an authentication standard that proves to inbox providers that ActiveCampaign is authorized to send email on your behalf. Without it, your campaigns are more likely to land in the spam folder or be rejected outright by corporate mail filters.

Think of DKIM as a digital signature your IT team adds to your DNS that says, "We authorize this platform to send email for us." DKIM is required by Gmail, Outlook, Yahoo, and most major inbox providers for bulk senders.

When using a sending subdomain, you can take advantage of reply-handling. Reply-handling allows mail to be initially processed by the Email Service Provider (ESP), which also manages opt-out requests, thereby making your emails CAN-SPAM compliant.

When a guest or customer clicks Reply on one of your marketing emails, that reply needs somewhere to go. By default, it goes to the sending address (such as marketing@email.yourbrand.com), which is not a real inbox unless your IT team creates one.

There are two options for handling replies:

Option A: Create a Dedicated Inbox at the Subdomain (Recommended for most teams)

Your IT team sets up a mailbox directly on the subdomain, such as marketing@email.yourbrand.com or replies@email.yourbrand.com. This option keeps campaign replies separate from other inboxes but requires human monitoring.

Option B: Route Replies to an Existing Inbox

Your IT team configures the subdomain to forward replies to a monitored corporate inbox, such as marketing@yourbrand.com. This option does not require a new inbox to manage because replies go where your team already works.

You must inform your IT contact about which reply-handling option you prefer. The Inntopia team will provide the DKIM records and confirm the reply address with you before go-live.

You must also contact Inntopia to let them know which option you prefer so it can be properly set up in ActiveCampaign.

ActiveCampaign uses CNAME records to authenticate your sending domain. The Inntopia team will provide these records to you from ActiveCampaign so you can add them to your DNS zone.

You will receive two DKIM CNAME records for the sending subdomain (e.g., email.yourbrand.com). These records allow ActiveCampaign's infrastructure to sign outbound mail on your behalf, satisfying DKIM authentication requirements enforced by Gmail, Outlook, Yahoo, and most enterprise mail filters.

Inntopia recommends configuring a dedicated subdomain for sending (ex: email.yourbrand.com. This subdomain cannot be one that is already in use. The exact name can be adjusted if your DNS zone has constraints.

You do not need to host anything at this subdomain or configure it as a web address. The provided CNAME records establish it for mail authentication purposes.

The general steps for configuring a new subdomain are as follows:

1. Receive DNS records from Inntopia:
   • These records include CNAME records to support services such as DKIM, MX records for supporting email delivery and TXT records to support SPF and DMARC.
2. Log into the management portal of your public DNS provider and select the option to create or add a new domain.
   • This portal is where your domain's DNS zone is managed and could be your domain registrar (GoDaddy, DigiCert, NetworkSolutions.com, etc.), your hosting provider, or a dedicated DNS service such as Cloudflare or Route 53.
3. In the DNS portal, add the CNAME records:
   •  For each record provided, enter the following information:
     • Record type – CNAME
     • Host / Name – As provided by Inntopia (e.g., dkim1._domainkey.email)
     • Value / Points to – As provided by Inntopia (the ActiveCampaign authentication endpoint)
     • TTL – 3600 (or your zone default)
4. Save and notify Inntopia.
   • Once the DNS records have been saved, notify Inntopia. DNS changes propagate globally within a few minutes to 48 hours depending on your TTL settings. Inntopia will monitor verification from ActiveCampaign and confirm when the authentication process is complete.

To configure a destination for replies to a campaign, choose from the three configuration options described below. Inform Inntopia of your chosen configuration so the Reply-To address can be configured to match in ActiveCampaign.

Two of the options require using a Mail Exchanger (MX) record. MX records direct email to the appropriate mail server responsible for receiving messages on behalf of a domain.

Option A: Dedicated Mailbox (Recommended)

Add an MX record for the sending subdomain pointing to your existing mail provider and create a dedicated mailbox (e.g., marketing@email.yourbrand.com). This option is useful if your team wants to keep campaign replies separate; however, it does require someone to monitor the inbox.

1. Enter the following information:
   • Record type – MX
   • Host – email.yourbrand.com
   • Value – Your existing mail server (e.g., your Microsoft 365 or Google Workspace MX endpoint)
   • Priority – 10 (or match your existing records)
2. Configure the dedicated email account in your mail admin console (Microsoft 365 Admin Center, Google Admin, etc.).
3. To confirm that the reply-handling option is working correctly, send an email to the new mailbox.

Option B: Forward Via MX Record

Add an MX record to the sending subdomain pointing to your existing mail provider. Then configure a catch-all forwarder or alias so any mail sent to *@email.yourbrand.com is routed to a monitored inbox (e.g., marketing@yourbrand.com). With this option, no new mailbox needs to be managed.

1. Record type – MX
2. Host: – email.yourbrand.com
3. Value – Your existing mail server (e.g., your Microsoft 365 or Google Workspace MX endpoint)
4. Priority – 10 (or match your existing records)
5. Configure the catch-all or alias in your mail admin console (Microsoft 365 Admin Center, Google Admin, etc.).
6. To confirm that the reply-handling option is working correctly, send an email to the new alias or distribution list.

Option C: Reply-To Header Only (No MX Record Needed)

This option does not use an MX record. Inntopia configures ActiveCampaign to set a Reply-To header pointing to a main-domain address (e.g., marketing@yourbrand.com). When the recipient clicks Reply, their mail client sends a response directly to that address, bypassing the subdomain.

This is the lowest-effort option and works well if reply volume is low.

If your domain already has an SPF record for the root domain, no changes are needed for the subdomain — CNAME-based DKIM handles authentication for the sending subdomain independently. If you have questions about your existing SPF configuration, contact Inntopia to review.