Unitpost vs AgentMail

AgentMail is an email API for AI agents: each agent gets its own inbox, created by API, for two-way threaded conversations rather than one-way notifications. Unitpost covers transactional and marketing email in one product with unlimited contacts on paid plans and a free tier of 5,000 emails a month. Across 8 compared capabilities, Unitpost leads on 3 and AgentMail leads on 2.

Which should you choose?

Choose AgentMail if

Each agent needs its own mailbox and two-way threads, more than you need to send to a customer list
You create inboxes per user or per tenant at scale
You want inbound mail over WebSockets without a public endpoint

Choose Unitpost if

Your agent sends your product's mail to your users: receipts, resets, notifications and campaigns
You want a free plan without a footer, on your own domain
You want marketing email, templates and SMS on the same contacts and bill
You want every agent send to pass the same checks as the API: verified domain, suppressions, topics and approval

What AgentMail does well

Stated plainly, because a comparison that pretends otherwise is not worth reading.

Inboxes created by API, thousands at a time, each with its own address
Threads, reply and reply-all built in, with the new text extracted from quoted history
Inbound pushed over WebSockets, so an agent needs no public webhook URL
A hosted MCP server with OAuth and 47 tools, including drafts and calendars
Inbound prompt-injection scanning (Agent Armor) and per-tenant isolation (Pods)

Pricing and free tier

Unitpost: 5,000 emails/month, 200/day, no credit card; On paid plans your monthly price is a sending allowance you spend at your tier's rate, and it refreshes every month. Marketing and unlimited contacts are included rather than billed as add-ons.
AgentMail: 3 inboxes, 3,000 emails a month (100 a day), no custom domains, with a "Sent via AgentMail" footer; Priced by inboxes, domains and sends: Developer is $20 a month for 10 inboxes and 10,000 emails, with add-ons per inbox, domain or 1,000 emails.

AgentMail pricing and free-tier details last verified 2026-11. Providers change these often — check their pricing page before making a decision.

Feature comparison

Feature and pricing comparison between Unitpost and AgentMail
Capability	Unitpost	AgentMail
What it's built for	An app's email and SMS to its users, with agents as one more client	Mailboxes for agents: create, receive, thread and reply
Free plan	5,000 emails/month, 200/day, no credit card	3 inboxes and 3,000 emails a month, 100 a day, no custom domains, with a footer
Receiving and threads	Receiving on your verified domain, with replies threaded by in_reply_to	Inboxes and threads as API resources, with reply, reply-all and forward
Marketing email and templates	Campaigns, segments, topics and templates	Not offered
SMS	On paid plans, on the same contacts and key	Not offered
MCP server	Hosted, OAuth, one tool per API operation, every send through the sending gate	Hosted, OAuth or API key, 47 tools
Idempotency keys on send	Idempotency-Key on sends, 24-hour dedupe window	Idempotency-Key on sends, replies and forwards, kept 24 hours
Dedicated IPs	Not launched yet	Enterprise, through sales

How do I switch from AgentMail?

There is no one-key importer for AgentMail: export your contacts and suppressions, import them, verify your sending domain, and move one kind of mail at a time.

Inboxes map to addresses on a verified domain with receiving turned on: replies reach your webhook as email.received, and the agent answers with in_reply_to to stay in the thread.

Read the docs

Frequently asked questions

Is Unitpost an AgentMail alternative?

For agents that send your product's email to your users, yes: one API for transactional, marketing and SMS, with every agent send checked like any other. If each agent needs its own mailbox with threads and inbound over WebSockets, AgentMail is built for exactly that.

Can an agent receive and reply to email on Unitpost?

Yes, on your own domain: turn on receiving for a verified domain, subscribe a webhook to email.received, read the message over the API, and reply with in_reply_to so mail clients thread it.

Switching from AgentMail?

Try it on the free tier first

5,000 emails a month free. Verify a domain, send a test, preview the migration.

Start for free Explore the docs