Microsoft Graph can drive a mailbox for an agent, at a licence per agent. MCPmailer gives agents addresses without seats or tenant admin.
Human mailboxes · Outlook and Microsoft 365 claims checked July 2026
Microsoft Graph exposes mail on a 365 tenant, and unlike Gmail it has a genuine application-permission path, so a daemon can send as a mailbox with no human present. In an enterprise already on Microsoft, it is the path of least resistance and the compliance story is strong.
If the agent must work inside employees' real mailboxes, or compliance requires everything to stay in your tenant under its retention and eDiscovery, use Graph. A shared mailbox plus application permissions is a legitimate design and we would not argue with it.
Every agent mailbox is a licence and an admin conversation, application permissions are famously hard to scope narrowly, and the throttling is written for humans. Nothing in Graph models reply-first quotas or an agent that should block until a customer answers. Addresses on a subdomain you control need no seats and no consent cycle.
Mail.Send as an application permission is typically tenant-wide unless you fence it with an application access policy, which is an extra artefact somebody has to maintain and audit. A key here reaches exactly one mailbox, and other identities in the workspace are invisible to it. The containment is the default rather than the configuration.
A mailbox is a licence. Ten agents is ten licences, before any of them sends anything. We charge a base plan plus the mail that moves, so a fleet of small agents is priced like the traffic it generates.
Graph throttles on human-shaped patterns, and there is no notion of a reply versus a cold send, no blocking wait, and no agent-readable refusal. Change notifications require a public endpoint and renewal. wait_for_reply is one outbound call.
Every row is a claim we could defend with their documentation open beside it. Where they are ahead, the row says so.
Nobody should move their people. Move the automation off the seats.
Keep humans on 365
Mailboxes, calendars, Teams, and your compliance posture stay exactly where they are.
Give agents a subdomain
agents.yourcompany.com, DKIM signed, entirely separate from the domain your staff send from.
Retire the app registration
The application access policy, the secret rotation, and the change-notification endpoint all go away.
Escalate into the tenant
The agent can hand a thread to a person by mailing them, and the whole conversation stays readable in the dashboard.
No. Your people keep their mailboxes. Agents get separate addresses on a subdomain, so agent mail never touches the mailboxes your business runs on.
Yes, with application permissions and ideally an application access policy to fence it. Budget a licence per agent and expect human-shaped throttling.
Microsoft is stronger here and we would say so. We keep full thread history, delivery events, and an audit trail, with audit logs and a DPA on higher plans, but Purview is a different class of tool.
Yes, by mailing them like anyone else. The thread stays readable in the dashboard, so the handover carries its context.
Your people keep their mailboxes. Your agents get their own, on a subdomain, with keys you can revoke one at a time and quotas written for software.
The free tier is 3,000 emails a month across three agent inboxes, no card, with receiving, threading, and search included. Enough to watch a real conversation happen before you decide.
More Human mailboxes