Pay for what your agent ships.

Self-serve only: no procurement, no “contact us for Enterprise”, and no sales team to call.

Your agents send 1,000 emails and receive replies a month

Free

$0 / mo

3,000 emails / month

3,000 inbound replies / month

  • 1 agent
  • TypeScript + Python SDKs, REST
  • MCP server
  • Magic-link signup, no card
Get API key

Pro

$20 / mo

50K emails / month

50K inbound replies / month

  • Send from your own domain (agent@yourcompany.com)
  • 5 agents
  • HMAC-signed webhooks + SDK reactor
  • Injection scan on every inbound
  • Email support
Start with Pro

Scale

$99 / mo

250K emails / month

500K inbound replies / month

  • Unlimited agents — no per-inbox pricing
  • Send from your own domains
  • Per-agent allowlists + send limits
  • Dedicated IP add-on (on request)
  • Priority support
Start with Scale

Enterprise

Self-serve

No Enterprise gate

All on the self-serve Scale plan

  • Single sign-on with any OpenID Connect provider
  • Enforce, so your provider is the only way in
  • New people join as members, never as admins
  • DPA on request
  • Dedicated IP add-on (on request)
  • Priority support
Learn more

Emails, inbound replies, and classification

Emails

Each recipient counts as one email, so a message to two addresses counts as two, whether they are in to, cc or bcc. Sending stops at your plan’s monthly cap until the next billing cycle or an upgrade, and the dashboard warns you at 80%.

Inbound replies

An inbound reply is one message delivered to one of your agents. It includes the parse to a structured payload, the injection scan, the sender-reputation lookup and webhook delivery. Inbound replies over the cap are still stored, but they are not scanned or sent to your webhook.

Classification · no extra charge

On paid plans, an optional classify step extracts intent, entities and urgency from first-contact mail (message.received) with our 2-call classifier (opt-in per agent). If your agent already runs an LLM on every new message, leave classification off: you don’t need the work done twice. If you want fast routing (switch (event.intent) with no extra LLM call), turn it on and we’ll do the extraction once for you.

Add-ons

Dedicated IP · On request, Scale plan

For teams that want reputation isolated from the shared pool. It is ramped by your own real traffic, with no seed network and no schedule we can fake, and you request it through the contact form, on Scale, with no contract negotiation. It is optional: most senders stay on the shared pool. Worth saying plainly: an IP only earns a reputation from sustained volume, so below a few hundred thousand messages a month the warm shared rail delivers better than your own cold IP.

Sending & receiving

FeatureFreeProScaleEnterprise
3,000 + 3,00050K + 50K250K + 500K250K + 500K
305002,0002,000
3005,00020,00020,000
15UnlimitedUnlimited
IncludedIncludedIncludedIncluded
Not includedIncludedIncludedIncluded

Safety & deliverability

FeatureFreeProScaleEnterprise
IncludedIncludedIncludedIncluded
IncludedIncludedIncludedIncluded
IncludedIncludedIncludedIncluded
IncludedIncludedIncludedIncluded
IncludedIncludedIncludedIncluded
Not includedIncludedIncludedIncluded
Not includedNot includedOn requestOn request
Not includedNot includedIncludedIncluded

Developer tools

FeatureFreeProScaleEnterprise
IncludedIncludedIncludedIncluded
IncludedIncludedIncludedIncluded
IncludedIncludedIncludedIncluded
Not includedIncludedIncludedIncluded

Billing

FeatureFreeProScaleEnterprise
$0$20$99$99
Not included$200$990$990
NoYesYesYes

Frequently asked questions

Do I need a card to start?
No. The Free plan starts with a magic-link signup and no card: 3,000 emails and 3,000 inbound replies a month, and one agent. It sends from a shared address such as hello.yourcompany@send.mails.ai, with zero DNS setup.
How does billing work?
Every plan counts two things, emails and inbound replies, each with its own monthly allowance. All billing runs through Stripe. Monthly plans bill in advance and there is no annual commitment.
Can I pay yearly?
Yes. Pro is $200 a year and Scale is $990 a year, which is two months free. Pro and Scale raise both allowances, billed monthly or yearly.
What happens when I reach my monthly cap?
Sending stops at your plan’s monthly cap until the next billing cycle or an upgrade, and the dashboard warns you at 80%. Inbound replies over the cap are still stored, but they are not scanned or sent to your webhook.
What do different agent shapes actually cost?

List prices for four agent shapes, side by side, from each vendor’s pricing page, checked October 2026. Mails.ai comes out cheapest when an agent receives a lot of mail; for send-only volume, a sending service is cheaper. Resend and Postmark count received email toward the plan; mails.ai counts it separately.

  • 10/day support agent (10 emails + 5 received per day; ~450 emails/mo): Mails.ai Free at $0/mo, Resend $0/mo (Free), Postmark $16.50/mo (Pro, for inbound). Both free tiers cover this. Mails.ai also scans every received email for prompt injection.
  • Bursty incident-response agent (Quiet most days, 200 emails in an hour on incident days; ~600 emails/mo): Mails.ai Pro at $20/mo, Resend $20/mo (Free stops at 100/day), Postmark $15/mo (Basic). Our Free tier sends 30 emails an hour, so a 200-email burst needs Pro. For send-only bursts, Postmark is cheapest.
  • 1k/day inbox-automation agent (1,000 emails + 5,000 received per day; ~30K emails + 150K received/mo): Mails.ai Scale at $99/mo, Resend $107/mo (Pro 100K + overage), Postmark $198/mo (Pro 125K + overage). Resend and Postmark count every received email toward your plan. Mails.ai Scale includes 500K received, each one injection-scanned.
  • 100k/mo notifications agent (100K emails + 20K received/mo; ~120K emails/mo): Mails.ai Scale at $99/mo, Resend $53/mo (Pro 100K + overage), Postmark $126.50/mo (Pro 125K). For send-heavy notifications, Resend is cheaper. Mails.ai is priced for agents that read and answer their mail.

For what agents do with an inbox, see the use cases.

What does the money pay for?

Custom-domain mail leaves through mail servers we run ourselves, not through a third party’s sending API. The full provider architecture, and the failover plan for the shared rail, are documented on the architecture page.

Every send is checked before it leaves our system: a per-agent reputation classifier scores what goes out, and suppression runs at send time so known-bad recipients never get a message. The classifier is invisible to your code: it’s deliverability infrastructure, not a product axis you have to choose between.

A per-sender cron monitors complaint and bounce rates every 15 minutes. Any sender crossing a 0.3% complaint rate gets paused before the upstream provider flags it at 0.5%, so one sender’s complaints are contained before they reach the pool you share. For teams that want reputation isolated from the shared pool, the Dedicated IP add-on is available on request (Scale).

In numbers: the complaint sweep runs every 15 minutes, the auto-pause threshold is 0.3%, and the injection scan looks for 6 kinds of injection.

Is there an Enterprise plan?
No. Scale is our largest plan: 250K emails and 500K inbound replies a month, with unlimited agents. Above that there is no self-serve plan yet; email support@mails.ai with your volume.
What does a dedicated IP cost?
It is available on request on the Scale plan rather than as a priced add-on, because the answer depends on your volume. If you are well under a few hundred thousand messages a month, the honest answer is that you do not need one. The dedicated IP page explains when it helps.
Can I use my own domain instead of the shared mails.ai address?
Yes — on any paid plan. Add your domain in the dashboard and we return the DKIM, SPF and DMARC records to create at your own registrar. Records only: no nameserver move, and if you already publish SPF or DMARC we tell you to merge rather than replace, so your existing mail keeps working. Verify, then create agents on that domain and they send as agent@yourcompany.com, DKIM-signed with a key generated for your domain. One current limitation: custom-domain sends cannot yet reach Outlook and Hotmail recipients — mail from your shared mails.ai address is unaffected.
What’s the difference vs AgentMail?
AgentMail provides programmatic agent inboxes — the same primitive. The differences, checked October 2026: mails.ai scans every received email for prompt injection by default, on every plan, while AgentMail’s screening (Agent Armor) is a beta you request, and it starts in observe-only mode. Each mails.ai agent can carry its own daily and hourly send limits, and Scale includes unlimited agents; AgentMail’s $20 plan has 10 inboxes and its $200 plan has 150, with $2-a-month add-ons in between. Both are self-serve, and both have allow and block lists.
What stops a customer from abusing the API to send spam?
Open signup is not open sending. (1) Signup is self-serve and sending starts immediately — there is no approval queue. What is gated is the CONTENT: every send is classified before it leaves, and cold outreach and bulk marketing are refused at the API with a 422 cold_email_prohibited, with a one-shot independent appeal for false positives. (2) Free tier hard-capped at 3,000 emails and 3,000 inbound replies a month, with email verification required. (3) Per-tier hourly + daily send caps in the billing layer. (4) A per-agent reputation classifier scores every send and suppression runs at send time. (5) Per-sender complaint cron auto-suspends anyone crossing a 0.3% rate. (6) Per-agent reputation, isolated per workspace, enforced on every send.
What if your upstream email provider cuts you off?
This is the reason we run our own mail servers as well as a shared upstream rail: custom-domain mail already leaves through mail servers we run ourselves (KumoMTA on dedicated servers we rent), not through a third party’s sending API. For the shared rail, a documented failover runbook to stand up backup senders with a roughly four-hour DNS swap is launch-hardening work. And the per-sender cron pauses anyone whose complaints cross 0.3% or bounces cross 5%, so reputation damage is contained long before an upstream escalates.

“Replies come back as events with an injection score already on them. We deleted a whole layer of parsing code the week we switched, and we gate on the quarantine flag, so our agent never sees the ones that look like attacks.”

Tomás VargaStaff Engineer, Cinderjay

“Moving our agent onto our own domain was a few DNS records at the registrar. No nameserver move, and our existing mail kept working. Replies to the agent still come back to its inbox, threaded with the message they answer.”

Ishani VaidyaCTO, Sedgequay

“Our agent writes every reply as a draft, with a key that can’t send. Someone on the team reads it and hits Send now in the dashboard.”

Marcus FeldFounder, Marrowkite

“Our tests send to the test address and wait for the real reply, so the whole loop is covered before a customer ever writes in. It answers in about a second, which keeps the suite fast.”

Ana Lucía RíosEngineering Lead, Gorsefinch

“Adding the MCP server was one JSON block. Claude Code could send and read its own inbox a minute later.”

Jonah AbramsDeveloper, Wickerjay

“A reputation score per agent tells us exactly which one needs attention, instead of one number for the whole account. It comes from each agent’s own replies, bounces and complaints, and we read it from the API.”

Mei Lin ZhouOperations, Larchwhistle

“Sends and replies have separate allowances, so a busy inbox never eats our sending quota. Pricing was the easy part.”

Kwabena AdomakoFounder, Oxbowlark

“Half our agents are LangGraph in Python and half are Node. Both SDKs make the same calls, so the team doesn’t have to think about it.”

Sofia BrandtEngineer, Moss & Ladder

“Signed webhooks, retries with backoff and an event id to dedupe on. The boring plumbing, done properly.”

Nikhil BhonsleBackend Lead, Thimblecrow

“We signed up, made a key and sent our first message without talking to anyone, and the free tier never asked for a card. That’s how infrastructure should feel.”

Frieda WesselFounder, Ploverwick Studio

Give your first agent an inbox

Free covers 3,000 emails and 3,000 inbound replies a month, with no card. Upgrade when your agents get busy.

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