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Custom domains let you create Mermail mailboxes on a domain your organization controls. Use them when an agent needs an address that matches your product, team, or company identity. Mermail provisions custom domains through Resend and returns the DNS records you need to publish. After the domain is verified, you can create mailboxes such as [email protected].

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Before you begin

You need:
  • A Developer or Enterprise workspace with an available custom-domain slot.
  • Workspace admin access.
  • Permission to edit DNS records for the parent domain.
  • A dedicated subdomain with at least three labels, such as mail.example.com or support.mail.example.com.
Mermail does not accept a bare root domain such as example.com. Use a dedicated subdomain so you do not replace the MX records that route your organization’s existing email.

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Add and verify the domain

1

Choose a dedicated subdomain

Choose the exact subdomain that should appear after @ in the new mailbox addresses.For example, registering mail.example.com lets you create an address such as [email protected].
2

Add the domain to your workspace

Open the Mermail console, select the workspace, and go to its custom-domain settings. Add the complete subdomain, including the parent domain.Mermail creates the provider domain and displays the DNS records required for verification.
3

Publish DNS records

Open the DNS dashboard for the parent domain. Create every record shown in Mermail and copy each field exactly.DNS providers format record names differently. Some expect the complete name, such as resend._domainkey.mail.example.com. Others expect only the part relative to the parent zone. Follow your provider’s convention and confirm that it does not append the parent domain twice.
Keep any existing DNS records that are not replaced by the records Mermail returns. Do not add guessed SPF, DKIM, MX, or DMARC values.
4

Wait for DNS propagation

DNS changes may appear within minutes but can take longer depending on the provider and record TTL. Review the published records before starting verification.
5

Verify the domain

Return to the domain in Mermail and click Verify. Mermail asks Resend to check the current DNS records.If the domain remains pending, wait for propagation, compare each record with the values shown in Mermail, and verify again. Review last_error when Mermail displays a provider error.
6

Create a mailbox

Wait until the domain status is verified, then follow Create a mailbox and select the verified domain for the address.
The domain is ready when its status is verified and Mermail shows a verification time.

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Understand domain status

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Manage an existing domain

You can list, verify, and delete custom domains from the workspace. Verification is safe to retry after you correct DNS records or wait for propagation. Before deleting a domain, remove every mailbox that uses it. Mermail rejects deletion while a mailbox is still attached to the domain.
Deleting a domain removes its Mermail and provider configuration. Confirm that no active mailbox or integration depends on it before you proceed.

Domains API reference

Open the Domains group in the API Reference to list, add, verify, or delete domains programmatically.

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Domain requirements

  • The value must be a subdomain, not a bare root domain.
  • The subdomain must contain at least three labels.
  • Each DNS label must use letters, numbers, and hyphens.
  • The workspace must be on a plan that includes custom domains.
  • Adding, verifying, and deleting a domain requires workspace admin access.
  • You must remove mailboxes from a domain before deleting the domain.

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Troubleshooting