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Custom domains let your workspace mailboxes use an address on a domain your organization controls, such as [email protected]. Mermail provisions the domain through the Email module, generates the DNS records you need to publish, and checks them for you. When the domain is fully connected, every mailbox in the workspace moves to it. A mailbox keeps its username, so [email protected] becomes [email protected]. Existing mail stays in place. Review all workspace mailbox addresses before connecting the domain; this change is not limited to your support mailbox.

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Before you begin

You need:
  • A workspace on a paid plan, such as Developer. Each workspace supports one custom domain.
  • Workspace admin access. Other members can view the setup but cannot add, check, or remove a domain.
  • Permission to edit DNS records for the domain.
Use a dedicated subdomain, such as mail.example.com. Mermail does not accept a domain that already receives email, so a subdomain keeps your existing company email untouched.

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Open Custom Domains

On the Mermail home page, find the Custom Domains card and click Open Custom Domains. The page belongs to the workspace you have selected and walks you through three steps. On the Free plan, the page shows Upgrade to Developer instead of the domain form. Your workspace keeps using its Mermail address until you upgrade.

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Connect your domain

1

Choose your domain

Under 1. Choose your domain, enter the domain or subdomain that should appear after @ and click Check domain.Mermail checks that the domain:
  • Is a valid domain, such as example.com or mail.example.com.
  • Is not already used by this or another workspace.
  • Does not already have email (MX) records.
If the domain is available, click Add domain. If it already receives email, Mermail shows the existing MX records and suggests a subdomain. Click Use mail.example.com (or the suggested name) to check it instead.
2

Add DNS records

Under 2. Add DNS records, Mermail lists every record to publish. Open the DNS dashboard for your domain and create each record exactly as shown. Use the copy button next to each name and value.DNS providers format names differently. Some expect the full name, such as selector._domainkey.mail.example.com. Others expect only the part before your zone. Follow your provider’s convention and check that it does not add the domain twice.
Set every CNAME record to DNS only. If your DNS provider offers a proxy (for example, the orange cloud in Cloudflare), turn it off for these records. A proxied CNAME returns IP addresses instead of the target and never verifies.
Keep existing DNS records that the list does not replace. Do not add guessed SPF, DKIM, or MX values.
3

Verify the connection

DNS changes can take a few minutes, or longer depending on your provider and record TTL. Under 3. Verify connection, click Check connection.Mermail re-checks every record and updates the Status column in step 2. For each record that is not verified yet, it looks up your public DNS and explains what it found, for example:
  • No CNAME record found at this name. The record is missing or has a different name.
  • Returns IP addresses instead of a CNAME. The record is proxied. Set it to DNS only.
  • Points to another target instead of the expected one. Correct the record value.
  • Found at name.example.com.example.com instead. Your provider added the domain twice. Enter the name without the domain suffix.
  • A TXT record exists but does not match the expected value. Replace the value with the one shown.
  • MX priority is 20; expected 10. Correct the MX priority.
Fix the records, wait for DNS to update, and click Check connection again.
The domain is ready when both Sending ready and Receiving ready appear and the step shows Ready. Mermail then moves workspace mailboxes to the domain.

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Understand the connection status

The domain card shows two capabilities: If only sending is ready, the domain is partially verified. Add the pending MX record, then check the connection again to receive email. Each DNS record also has its own status:

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What happens to your mailboxes

  • When the domain is ready, every mailbox in the workspace moves to the custom domain and keeps its username. New mailboxes are also created on the custom domain.
  • If an address is already taken on the domain, Mermail cannot move the workspace and shows a conflict message. Resolve the duplicate addresses, then check the connection again.
  • If the workspace moves to the Free plan, the domain is paused. Mailboxes return to a Mermail-hosted address until you upgrade again.

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Test your new address

Once both capabilities are ready:
  1. Open the mailbox you plan to use and confirm its custom-domain address.
  2. Send one test message to an external inbox you control. Check the sender, signature, and where the message arrives.
  3. Reply from that inbox and confirm the reply appears in Mermail.
  4. Update website contact links and other places that display the old address.
If either test fails, check the domain’s sending and receiving status before sending customer messages. Do not assume that delivery to one test inbox proves delivery to every recipient.

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Improve deliverability

Step 2 also shows a deliverability checklist:
  • SPF and DKIM: Mermail signs every message once the records above are verified.
  • DMARC: Mermail does not create this record. Add a TXT record at _dmarc.<your domain>. Start with a relaxed policy, such as v=DMARC1; p=none; rua=mailto:dmarc@<your domain>, then tighten it to p=quarantine and later p=reject.
  • Build sending history gradually: start with a small number of relevant messages to recipients who expect them. Increase volume only when delivery remains healthy. Pause and investigate bounces or complaints instead of following a fixed daily growth target.

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Remove a domain

Under 3. Verify connection, click Remove, type the domain name to confirm, and click Delete domain.
  • Every mailbox on the domain switches back to its @mermail.app address. If that exact address is taken, Mermail assigns a numbered variant.
  • Stored mail stays intact.
  • To use the domain again later, you must add and verify it from scratch.
Only one custom domain is supported per workspace. To use a different domain, remove the current one first.

Email module

Review send, receive, DNS verification, and attachment limits.

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Troubleshooting