# MCPmailer vs Fastmail

Fastmail has the best mailbox API of any human email host. MCPmailer is a mailbox built for an agent rather than a person.

Also searched as: Fastmail for AI agents, JMAP agent email, Fastmail alternative.

## What Fastmail is

Fastmail is the enthusiast choice: fast, private, no advertising, and the primary force behind JMAP, which is a genuinely modern mailbox protocol rather than IMAP with a hat on. It starts around sixty dollars a year for one person and has no free tier.

## Where Fastmail is the better choice

If a person is going to live in this mailbox, Fastmail is excellent and JMAP plus an app password is a pleasant way to automate around it. For a personal assistant working inside your own mail, it is a good pairing.

## Where MCPmailer differs

JMAP is a better mailbox protocol; it is still a mailbox protocol. It has no concept of an agent identity, a cold-send quota, a blocking wait, or a dashboard for someone supervising the agent, and every agent is another subscription.

### JMAP models a mailbox, not a conversation policy

You get efficient sync, push, and structured objects, which is a real improvement on IMAP. What you do not get is any notion that replying to an inbound thread is safe while emailing a stranger is not. That distinction is the whole basis of our quota model.

### No free tier to evaluate on

Fastmail is subscription-only, so trying an agent against it starts with a card and a per-user plan. Ours is 3,000 emails a month across three inboxes with no card, which is the difference between evaluating an idea and committing to one.

### One subscription per agent

Aliases are plentiful, but an alias is not an identity: mail to an alias lands in the same mailbox, under the same credential, with the same history. Separate agents that can be revoked separately means separate accounts, which means separate subscriptions.

## Using both

The split is the same as with any human host.

1. **You keep Fastmail** Your own mail, your own aliases, your own client.
2. **Agents get their own addresses** On a subdomain, with a key each, and nothing shared with your personal mailbox.
3. **The agent can still write to you** It emails you like anyone else, and the thread stays readable in the dashboard.

## Side by side (checked July 2026)

| | MCPmailer | Fastmail |
| --- | --- | --- |
| Built for | Software, not people. No seats, no consent screen, no inbox a human also lives in. | People who care about their mail. |
| Inbox per agent | One mailbox per agent with no licence attached, created in seconds, deleted as easily. | An account per agent, each a subscription. Aliases share one mailbox. |
| Receiving and threading | Inbound MX, parsed MIME, In-Reply-To threading. The whole conversation stays queryable. | Yes, with JMAP and IMAP access. |
| MCP server | Native. Streamable HTTP with a bearer key, or OAuth 2.1 for clients that cannot hold one. | No. |
| Waiting for a reply | wait_for_reply long-polls the mailbox until the other side answers, up to five minutes per call. | JMAP push, or polling. |
| Human oversight | A colleague can watch what the agent wrote without being given the mailbox. | Personal account settings. |
| Sending limits | Built for automation, so sending programmatically is the supported path rather than the terms violation. | Human-scale sending limits, and automation is not the target use. |
| Your domain | A subdomain for agents, kept away from the domain your people send from. | Your own domain supported. |
| Search | Full-text search across the workspace, exposed to the agent as search_inbox. | Excellent, within the account. |
| Beyond the inbox | A shared contact book with per-contact memory, notes, an encrypted vault, and a public hostname per agent. | Calendars, contacts, and notes for a person. |
| Free tier | 3,000 emails a month, 100 a day, 3 inboxes, no card. | No free tier. Trial only. |
| Content privacy | We never read message content and never train on it. Enforcement is behavioral and metadata only. | Strong, and a selling point. Per account, not per agent. |

## Questions

### Can an AI agent use Fastmail over JMAP?

Yes, and it is one of the nicer mailbox APIs to work against. You still build threading policy, cold-send controls, and supervision, and you pay per account.

### Are Fastmail aliases enough for several agents?

Not if you want them isolated. Aliases deliver into one mailbox under one credential, so revoking one agent or auditing it separately is not possible.

### Which is more private?

Fastmail is excellent on privacy and we would not claim to beat it for personal mail. For agent mail our position is narrower and specific: we never read message content and never train on it.

### Does MCPmailer support JMAP or IMAP?

No. The interfaces are MCP and a REST API, because both are what an agent can actually use without a MIME library.

All comparisons: https://mcpmailer.com/vs
Docs: https://mcpmailer.com/docs.md
Pricing: https://mcpmailer.com/pricing.md