AgentMail gives AI agents their own inboxes over an API. Brew lets an agent design, send and automate your customer email. When to use each, or both.
Brew publishes this comparison. We reviewed AgentMail's own website, pricing page and documentation on October 12, 2026; this is a documentation comparison, not a claim of hands-on testing. Check current plan limits on AgentMail's pricing page.
You are building an AI agent and it needs email. Maybe it should answer support questions, chase invoices or book meetings. Maybe it should send your onboarding sequence and the monthly newsletter. Search "email for AI agents" and AgentMail comes up, and so does Brew.
Both give an agent email over MCP and an API. They solve different problems. AgentMail gives an agent its own inbox, so it can hold conversations. Brew gives an agent your company's customer email to run: it designs finished, on-brand emails, sends them to your audiences and runs the automations. Some teams need one. Plenty need both.
AgentMail describes itself as "the first email provider built for AI agents". Its homepage calls it "the email inbox API for AI agents". The idea is that each agent gets its own email identity.
The core features, from its homepage and documentation:
AgentMail positions this against sending APIs. Its knowledge base says that "unlike transactional email APIs that focus on one-way sending, AgentMail is built for two-way agent communication". It also strips quoted history from replies and searches across all inboxes, which helps an agent that is reading mail all day.
Pricing is by inboxes and volume. The free plan has 3 inboxes, 3,000 emails a month and 100 a day, without custom domains. Developer is $20 a month for 10 inboxes, 10,000 emails a month and 10 custom domains. Startup is $200 a month for 150 inboxes and 15,000 emails a day. Enterprise is custom.
AgentMail does this job well. If your agent has to act like a person with a mailbox, it is built for that.
AgentMail's documentation covers inboxes, messages and conversations. Its docs index has no pages on email design or templates, contact audiences, scheduled campaigns or unsubscribe management for subscribers. Its Lists feature is an allow and block list for an agent's inbox, not a mailing list.
Its own deliverability guide points the same way. It tells you to start conversations, "not to close a sale in the first email". It warns that providers often flag emails that only include HTML. For volume, it suggests spreading sends across many inboxes rather than sending 10,000 emails from one.
That advice is sound for agent outreach and replies. It is the opposite of what a newsletter, a product launch or a designed onboarding sequence needs. Those emails go from one brand to many contacts, carry your layout and images, and need consent and unsubscribes handled for you. AgentMail's terms also list "spam, phishing, or unsolicited messaging" as a prohibited use.
Brew is an AI-native email platform. Your agent connects to it over MCP, from Claude, ChatGPT, Cursor or Grok, and runs your company's customer email:
On OAuth connections, a call that emails people returns a confirmation request first, so you approve before a campaign goes out. Developers get the same surface through a REST API, a typed SDK and a CLI. The MCP launch post explains how the connection works.
Pricing is based on sends and AI credits. You can start free with 500 AI credits and 1,000 sends a month. Growth is $99 a month for 10,000 credits and 50,000 sends. Pro is $249 a month for 25,000 credits and 200,000 sends.
What Brew does not do: give your agent an inbox to read and reply from. Brew's documentation has no inbound email feature. If the agent needs to hold conversations, use an inbox product for that part.
| AgentMail | Brew | |
|---|---|---|
| What it is | Inbox API for AI agents | Email platform your agent runs |
| Main job | Give an agent its own address to send, receive and reply | Design, send and automate your company's customer email |
| Receiving and threads | Yes, with webhooks and WebSockets | No inbound inbox |
| Email design | Not a design tool | On-brand emails generated from your brand |
| Contacts and audiences | Allow and block lists only | Yes, unlimited contacts |
| Campaigns and newsletters | None in its docs | Yes |
| Lifecycle automations | Build them in your own code | Yes, event-triggered flows |
| Transactional email | Sends through the API | Yes, through a transactional-purpose domain |
| Custom domains | Paid plans | Your own verified domain |
| MCP server | Yes | Yes |
| Pricing | By inboxes and volume; free plan, Developer $20/mo | By sends and AI credits; free to start, Growth $99/mo |
Choose AgentMail if the agent is a participant in conversations. Support agents, sales assistants that reply to leads, agents that sign up for services or handle scheduling over email. The hard part there is receiving, threading and replying, and AgentMail handles that.
Choose Brew if the agent is running your email program. Newsletters, product announcements, onboarding and win-back sequences, receipts. The hard part there is making each email look like your brand, sending to the right audience and keeping automations running. Brew handles that.
The two fit together without overlap. A typical setup for a SaaS product:
support@ on its own subdomain, handles conversations. It answers questions, books calls and follows up.fire_trigger_event and an idempotency_key. A published automation listening for that event runs the follow-up; updating a contact alone does not start it.Keep each tool on its own domain or subdomain, so conversation mail and bulk marketing mail build separate reputations. Decide which system owns marketing consent. An unsubscribe in Brew does not reach an AgentMail inbox on its own.
Only for part of the job. If you want your agent to send designed marketing and lifecycle email, Brew is the better fit. If you want your agent to have its own inbox and hold two-way conversations, Brew does not do that and AgentMail does.
It depends on the job. For an agent that receives and replies to email, use an inbox API such as AgentMail. For an agent that runs your newsletters, campaigns and automations, use an email platform with an MCP server, such as Brew.
Yes, if it works through a platform built for marketing email. Connect the agent to Brew over MCP and it can design an on-brand campaign, pick an audience and send from your domain. On OAuth connections, Brew asks for your confirmation before anything goes out.
AgentMail's docs do not describe newsletter features such as subscriber lists, templates or unsubscribe management. Its deliverability guidance is written for one-to-one conversations. Use a marketing platform for newsletters.
Yes. Use AgentMail for the agent's inbox and conversations, and Brew for designed lifecycle and campaign email. Keep them on separate sending domains and pick one system as the owner of marketing consent.
If your agent should be running your email program, connect Brew over MCP and ask it to build your first onboarding sequence.
