Choose the Email Address Your AI Agent Will Work From

Imagine a customer receives a useful answer from your AI agent and replies a week later. In the meantime, someone has changed the agent's software. The customer still expects the address in that conversation to reach your business.

That expectation is a good place to start when choosing an email identity for an agent. Before naming the assistant or connecting a model, decide which business responsibility the address represents and who will look after the conversations arriving there.

For a first project, I would give the agent a narrow role, a clearly described address, and a person responsible for it. That person should be able to explain where replies go even when the agent is unavailable.

Start With the Job the Address Represents

Suppose a small services company wants an agent to answer initial setup questions. It could describe the role as “setup inquiries” instead of giving the agent the founder's everyday mailbox and asking it to work out what matters.

That choice gives the team something specific to design. A message about supported setup options belongs in the workflow. A request to change a contract needs a different owner. A personal message intended for the founder should never have been part of this agent's work.

A role address can help people understand what to expect, but the name is only a label. Calling an address “setup” does not restrict which messages a connected application can read. The account, credentials, and tools determine that access. Likewise, giving an agent a person's display name does not establish who approved its actions.

Write down the role in ordinary language before choosing the address. A useful description might be: “This assistant helps people understand our published setup options and passes requests for commitments to the service team.” That is a proposed job description, not a capability that follows automatically from creating a mailbox.

Separate the Address From the Access Behind It

People use “identity” to mean several things. For this decision, keep three records distinct:

An email alias may route to a mailbox that already exists. It does not, by itself, create a separate permission boundary. Before using one, ask the administrator which underlying account receives the mail and what other correspondence the connected agent could reach. There may be a perfectly reasonable setup for the job; the address alone cannot tell you what it is.

Microsoft's least-privilege guidance for AI agents recommends a dedicated agent identity with a named owner, documented purpose, and a review of effective permissions across tools and systems. That is useful guidance for the access record. It does not mean that a contact address is itself a security principal, or that using a separate address completes the permission work.

Mailrun's communication identity is the part people contact. In the bring-your-own-agent setup, your application supplies the agent and its business instructions; Mailrun provides the communication channels. The Agent Identities overview describes keeping a Mailrun identity when the connected agent changes. That continuity applies within Mailrun. It is not a promise that another provider can take over the address, or that a new agent automatically inherits the old agent's task state.

Check the Reply Destination, Not Just the Display Name

Look at the message a recipient actually gets. The visible name, the From address, and the place a reply will go deserve separate attention.

RFC 5322, Section 3.6.2 defines the originator fields. Reply-To, when present, identifies the address or addresses to which the author suggests replies should be sent. Without it, replies should by default go to the From address. The specification describes message fields, not a guarantee that a particular recipient or application will follow the intended route.

For your first check, send an ordinary message to a mailbox your team controls and reply through that mailbox's normal interface. Confirm which business inbox receives the answer and who can see it. If the reply goes to a different address, record why and who owns that destination.

Choose a display name and introduction that accurately describe the assistant's role. I would make clear that the recipient is dealing with an AI assistant working for the business, and give them a practical way to reach a person. That is my recommendation for a legible customer experience, not a claim that a particular label settles every disclosure obligation.

Keep a Small Ownership Record

The record need not begin as a large system. For the setup-inquiries example, a short entry could contain:

• The address, its business purpose, and the person responsible for it.
• The application allowed to read or send, with a reference to its approved access rather than a copied credential.
• The place where incoming replies and unresolved conversations can be reviewed.
• The person who takes over when the question exceeds the role or the agent stops running.
• The process for reviewing this entry when the application or responsible person changes.

Keep the record somewhere the relevant team can access. Do not put keys or unrelated customer correspondence into it. If the application keeps pending tasks separately from the mailbox, note where those tasks live. A mailbox full of messages does not explain whether a promised follow-up is still waiting in another system.

The deeper permission checks belong in Test an AI Agent's Email Permissions Before It Sends. Here, the goal is to make the first design decision clear enough that the person connecting the agent knows which business role, address, and owner they are implementing.

Begin With an Address You Can Explain

If you are exploring Mailrun, the Free option in Agent Identity checkout is a starting point for evaluating the setup. Check the current package details there rather than assuming that phone service, a custom domain, or a particular allowance comes with it. Bring an agent and a narrowly defined email job; use the developer docs to choose a supported connection.

Before inviting real correspondence, ask a colleague to follow a controlled reply from the recipient's mailbox to the person responsible for it. They should be able to explain whose address it is, what the agent is there to do, and how a person takes over. Those answers make the address useful beyond the first demonstration.