When Should an AI Agent Use a Custom Email Domain?

Hosted inboxes are fast; custom domains add a business identity. Here is when each approach makes sense.

Start hosted when speed matters#

A hosted inbox removes DNS setup from the first experiment. It is a good fit for prototypes, internal automations and workflows where the address itself is not customer-facing.

Use a custom domain for external identity#

When an agent communicates as part of a company, an address on the company's domain is easier to recognize and keeps the identity aligned with the business.

DNS is part of the setup#

Custom email requires domain authentication and inbound routing. That normally means identity verification, DKIM records and an MX record. DMARC is also useful for domain protection and monitoring.

Verify inbound routing too#

Authentication alone does not prove that inbound email can reach the mailbox. A setup should confirm that the public MX record is active before declaring the domain ready.

Separate domain setup from mailbox creation#

Once a domain is verified, multiple agent mailboxes can be created beneath it. This keeps DNS configuration as a one-time domain task rather than something repeated for every agent.