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<!-- Last reviewed: 2026-08-25 -->

# Startup Mail vs AgentMail

> Compare Startup Mail and AgentMail for agent inboxes, company email, custom domains, APIs, webhooks, team access, and pricing.

Startup Mail and AgentMail both give software a real email address, provision inboxes through code, and isolate each agent with a mailbox-scoped key. The main difference is the surrounding workflow.

Choose Startup Mail when agents and people need to work in the same custom-domain mail system. Choose AgentMail when standard email protocols, WebSockets, or an agent-only platform matter more than a built-in human inbox.

## The short answer

Startup Mail combines a company mailbox with an agent control plane. It can create tenants and mailboxes through the API, issue tenant- or mailbox-scoped keys, hold drafts for review, schedule sends, and enforce address or domain policies. People can use the same system through its web inbox, team access, or forwarding.

AgentMail is email infrastructure built around agents. It also provisions inboxes on demand, separates customers, and limits keys to an inbox. Its clearest technical differences are WebSocket events plus IMAP and SMTP access.

Neither product is better for every use case.

## Startup Mail and AgentMail at a glance

| Capability                          | Startup Mail                             | AgentMail                                     |
| ----------------------------------- | ---------------------------------------- | --------------------------------------------- |
| Custom-domain sending and receiving | Yes                                      | Yes, on paid plans                            |
| Persistent threads                  | Yes                                      | Yes                                           |
| Built-in web inbox                  | Yes                                      | Console for management; IMAP for mail clients |
| Shared team mailbox                 | Yes                                      | Not its main product model                    |
| Private mailbox grants              | Yes                                      | Access is controlled through scoped API keys  |
| Gmail or Outlook forwarding         | Yes, with a protected reply route        | Not a documented core feature                 |
| REST API                            | Yes                                      | Yes                                           |
| TypeScript SDK                      | Yes                                      | Yes                                           |
| Python SDK                          | Source package; registry release pending | Yes                                           |
| MCP server                          | Yes                                      | Yes                                           |
| Signed webhooks                     | Yes                                      | Yes                                           |
| WebSockets                          | No                                       | Yes                                           |
| SMTP relay                          | No                                       | Yes                                           |
| IMAP                                | No                                       | Yes                                           |
| Programmatic inbox creation         | Yes                                      | Yes                                           |
| Multi-tenant customer isolation     | Tenants and mailbox-scoped keys          | Pods and inbox-scoped keys                    |
| Drafts and scheduled sends          | Yes                                      | Yes                                           |
| Address and domain policies         | Yes                                      | Yes                                           |
| Marketing campaigns                 | No                                       | No campaign product                           |

AgentMail details come from its [inbox capability guide](https://www.agentmail.to/docs/knowledge-base/inbox-capabilities), [permissions reference](https://docs.agentmail.to/permissions), [IMAP and SMTP guide](https://docs.agentmail.to/imap-smtp), and [Pods documentation](https://www.agentmail.to/docs/documentation/core-concepts/pods). We checked them on 25 August 2026. The older capability guide still says IMAP is coming soon, but AgentMail's dedicated IMAP guide and [June 2026 launch post](https://www.agentmail.to/blog/agentmail-now-supports-imap) document live support. We treat the older line as stale.

Startup Mail's provisioning, resource-scoped keys, drafts, scheduling, and policies are documented in the [agent inbox guide](https://staging.startupmail.dev/docs/agent-inboxes.md).

## Choose Startup Mail when people and agents share the work

Startup Mail treats the mailbox as a company resource.

A founder can read `hello@company.com` in the web inbox. The same address can forward to Gmail or Outlook. A teammate can answer from the shared mailbox. An agent can read or reply through the API or MCP.

All four routes use the same stored conversation.

This model suits a small company that wants one email system for ordinary work and software automation. You do not have to build a separate interface so a person can inspect the agent's conversations.

Private mailboxes use a second access boundary. A workspace administrator can manage billing or domain settings without gaining the right to read the founder's mail. The mailbox owner grants read or send access to specific people.

Choose Startup Mail for:

- A shared `hello@` or `support@` inbox
- A founder who wants company mail in Gmail
- An agent that drafts or sends replies under human oversight
- A product that reads incoming mail through an API
- A team that needs both shared and private addresses
- A company that does not need a full office suite

## Choose AgentMail when inboxes are part of your product

AgentMail remains the stronger fit when your product depends on standard mail protocols or persistent event streams.

Your application can create an inbox, assign it a custom address, and use a client ID to avoid duplicates. Pods can isolate inboxes, domains, threads, drafts, and API keys for each customer. Inbox-scoped keys can limit a service to one address.

Startup Mail now covers the corresponding control-plane work with tenants, idempotent mailbox provisioning, resource-scoped keys, drafts, scheduled sends, and mailbox policies. AgentMail's remaining advantages are useful when your application needs a protocol or event model Startup Mail does not provide.

AgentMail also supports WebSockets. A worker can receive events without exposing a public webhook endpoint. Startup Mail supports signed webhooks, but not WebSockets.

AgentMail is the better choice when you need:

- WebSocket event streams
- IMAP or SMTP access for an existing system
- A published Python package today
- AgentMail's Pod model or organization tooling
- Standard mail clients rather than a built-in web inbox

These are material differences. Startup Mail does not provide WebSockets, SMTP, or IMAP.

## Built-in human workflow is the clearest dividing line

AgentMail's documentation starts with the agent. It describes programmatic inboxes, real-time events, SDKs, scoped keys, and tenant isolation. AgentMail also supports IMAP and SMTP, so a person can connect Outlook, Apple Mail, Thunderbird, or another compatible client.

Startup Mail starts with the mailbox. Humans can use the web inbox or forward mail to an inbox they already know. Software can use the same messages through REST, the TypeScript SDK, the Python source package, webhooks, or MCP.

This affects how much you need to build.

If every message will be handled inside your own product or a standard email client, AgentMail's model is useful. If a founder or support lead needs a built-in shared web inbox with separate private-mailbox grants, Startup Mail provides that workflow directly.

Forwarding also lets a person reply from Gmail or Outlook through a signed, expiring relay. It does not synchronize folders, read state, or labels. It is a delivery route, not IMAP.

## Permissions take different forms

Both products support limited credentials.

AgentMail has a detailed permission system. Keys can be scoped to an organization, Pod, or inbox. A permissions whitelist can restrict actions such as reading messages, sending mail, managing drafts, or creating webhooks.

Startup Mail keys can be scoped to an organization, tenant, or one mailbox. A single capability allowlist narrows actions inside that resource boundary.

Both products can now isolate one agent credential from other inboxes. Startup Mail additionally connects that boundary to its human team and private-mailbox model. AgentMail connects it to Pods and its agent-focused organization model.

## Pricing

[AgentMail's pricing](https://www.agentmail.to/pricing) includes a free plan with three inboxes, 3,000 emails per month, and 3 GB of storage. Its Developer plan costs $20 per month and includes 10 inboxes, 10,000 emails, 10 GB of storage, 10 custom domains, and two organization seats. Developer and Startup customers can add one inbox, one custom domain, or 1,000 monthly emails for $2 per month. Annual billing is 20% less than monthly billing.

Startup Mail costs $2 per month or $12 per year for 1,000 email events per month. An incoming delivery, each outbound recipient, and each forwarded copy count as events.

The units are different, so a headline price comparison can mislead.

AgentMail gives more included email volume and a free route for small agent projects. Startup Mail costs less for a low-volume company mailbox that needs human access. A platform that creates many inboxes should compare the full number of addresses, messages, domains, seats, and stored data.

## Can you use both?

Yes.

A company could keep shared and private company mail in Startup Mail while giving autonomous product agents separate AgentMail inboxes.

This split can make sense when company mail needs Startup Mail's human workflow while a product agent needs AgentMail's WebSockets, IMAP, or SMTP. It can also keep an experimental agent fleet away from founder correspondence.

The cost is another integration and another place to manage domain records, credentials, retention, and abuse controls.

## Which should you choose?

Choose Startup Mail if the address belongs to a company and must work for both people and software.

Choose AgentMail if each inbox is agent-only and your application benefits from WebSockets, IMAP, or SMTP.

For a shared company inbox with agent help, Startup Mail is the simpler fit. For an agent platform built around WebSockets, standard mail protocols, and customer Pods, AgentMail has the stronger fit.

## Frequently asked questions

### Is Startup Mail an AgentMail alternative?

Yes. Both products now support programmatic inboxes, isolated credentials, drafts, scheduling, and communication policies. Startup Mail does not replace AgentMail's Pods, IMAP, SMTP, or WebSockets.

### Can both services receive email?

Yes. Both store messages, group replies into threads, expose APIs, and send real-time webhook events.

### Which service is better for a human support team?

Startup Mail has the clearer fit when the team wants a built-in web inbox, shared mailboxes, private mailbox grants, and Gmail or Outlook forwarding. AgentMail can instead connect to standard mail clients through IMAP and SMTP.

### Which service is better for an agent SaaS product?

It depends on the product. Startup Mail fits an agent SaaS that also needs a human web inbox and company-mail workflow. AgentMail fits one that needs WebSockets, IMAP, SMTP, or its Pod model.

### Does Startup Mail support SMTP or IMAP?

No. Startup Mail uses its web inbox, forwarding, REST API, TypeScript SDK, webhooks, and MCP. AgentMail supports both SMTP and IMAP.

### Which product costs less?

It depends on the workload. Startup Mail is inexpensive for a low-volume workspace. AgentMail has a larger free allowance and clearer plans for multiple agent inboxes. Compare usage with each provider's counting rules.

## Related reading

- [The complete guide to email for AI agents](https://staging.startupmail.dev/guides/email-for-ai-agents.md): Learn how to give an AI agent a real mailbox with scoped access, durable threads, safe sending, webhooks, MCP tools, and human review.
- [How to give an AI agent an email address on your domain](https://staging.startupmail.dev/guides/give-ai-agent-email-address.md): Set up a custom-domain mailbox for an AI agent with safe DNS changes, narrow permissions, MCP or webhook access, and human approval.
- [Inbound email webhook vs persistent mailbox: which do you need?](https://staging.startupmail.dev/guides/inbound-email-webhook-vs-persistent-mailbox.md): Compare inbound email webhooks with persistent mailboxes, including storage, threads, retries, human access, and the cases where you need both.