Mails.ai

Mails.ai is an email API for applications and AI agents that need to send messages and process replies. It is best suited to developers building transactional or conversational workflows, not sales teams running cold outreach. Its structured inbound data and injection scanning are useful strengths, while hard caps and shared-pool sending shape its production fit.

Overview

Mails.ai turns incoming email into a payload with sender, subject, body, headers and attachments, plus an injection score and sender reputation. That gives an agent more context for handling a reply while flagging a risk that plain message parsing would miss. Injection scanning is included on every plan.

Classification can extract intent, entities and urgency, but it is opt-in at $0.003 per inbound. Teams that need those fields should account for the added per-message cost rather than assume classification comes with the base service. Mails.ai supports transactional and conversational email and refuses cold outreach at the API, which rules it out for prospecting campaigns.

Key features

Developers can connect through REST, webhooks, an MCP server, or TypeScript and Python SDKs. Named integrations include Claude Code, Cursor, Cline, Continue, Windsurf, OpenAI Agents SDK, Anthropic SDK, LangGraph, Mastra, Vercel AI SDK and Pydantic AI. This makes the service relevant to teams building agent workflows in a range of coding tools and frameworks; the early, self-serve product is less compelling to organizations that need a mature platform.

On transport and storage, the maker says public surfaces use TLS 1.3, the primary database is encrypted at the infrastructure layer, and AWS SES message storage uses AWS-managed KMS encryption. Mails.ai describes its baseline as GDPR-aligned, but does not have SOC 2 today and excludes HIPAA from Phase 1 scope. Organizations with those compliance requirements should look elsewhere.

The service does not offer email warm-up, mailbox rotation or multichannel outreach. Sending is currently through a shared pool; a dedicated IP is an on-request roadmap add-on on Scale+ at $50 per month per IP, not a current sending option. That distinction matters for teams seeking dedicated sending infrastructure.

Pricing

The free plan costs nothing (billed $0/mo) and includes 3,000 events per month, one agent, TypeScript and Python SDKs, REST, and the MCP server, with no card required. It is a practical way for a solo developer to start, but its event cap and single-agent limit constrain broader use.

Pro costs $20 a month (billed $20/mo) and raises the allowance to five agents, 50K sends and 50K inbound replies per month. It adds a custom domain and email support, making it the more suitable tier for a small team with moderate volume.

Scale costs $99 a month (billed $99/mo) and includes unlimited agents, 250K sends, 500K inbound replies, per-agent allowlists and budgets, and priority support. It suits larger deployments that need more volume and agent-level controls, though its sending still uses the shared pool.

Caps have operational consequences: sends stop when the monthly plan cap is reached, and inbound replies above the cap are stored but not scanned or sent to the webhook. Teams relying on timely automated processing should size their plan with headroom; stored replies alone do not preserve the workflow.

Platforms

Mails.ai is available on web and through an API. Its SDKs, webhooks and MCP server provide programmatic access for teams integrating email into their own applications.

Who it's for

Mails.ai is a strong fit for developers who want an API-centered way to send transactional or conversational email and pass structured replies into agent workflows. The free plan offers a low-commitment starting point, while Pro and Scale provide higher quotas and more agents. It is not suitable for cold-email prospecting, and its current shared-pool sending and compliance gaps may rule it out for some production environments.

Pros and cons

Pros

• Structured inbound payloads include message fields, attachments, injection score and sender reputation, giving developers useful material for safer reply handling.
• Injection scanning applies on every plan, including free, rather than being reserved for higher tiers.
• REST, webhooks, MCP and two language SDKs support several integration approaches, with named connections across agent frameworks and coding tools.
• The free tier has no card requirement, while paid plans publish clear monthly agent and message limits.

Cons

• Cold outreach is refused at the API, so it cannot serve as a prospecting platform.
• Monthly send caps stop sending, and inbound overages lose scanning and webhook delivery, which can interrupt automated workflows.
• Dedicated IPs are a roadmap add-on and current beta sending uses a shared pool.
• No SOC 2 today and no HIPAA scope in Phase 1 make it unsuitable for some regulated teams.
• Classification costs an additional $0.003 per inbound, and email warm-up, mailbox rotation and multichannel outreach are absent.

Alternatives

For a directory of prospecting-focused products, see Cold Email Software; Mails.ai itself does not support that use case.

Choose Mixmax if tracked email and sequences are a better match: its free plan includes 20 tracked emails per month and up to 50 sequence recipients per month. Yesware is another option for teams prioritizing basic open and attachment tracking, with a free plan that includes 10 campaign recipients per month and a meeting scheduler.

Growbots may suit prospecting teams seeking email accounts, sequences and partial access to a prospects database on its free plan. Mystrika is an alternative with a free plan. Outplay offers a free plan for one user, two mailboxes and 2,000 active prospects per month.

ReachInbox is an alternative with an API and web access; its Starter Plan is $30 a month (billed yearly) and includes 10,000 emails per month and 2,000 active leads per month. Regie.ai may fit teams seeking a free pool of 250 one-time credits per person for research, enrichment, drafting and agents. For mailbox warm-up, consider Warmbly, which offers a free pool for up to 10 mailboxes and an unlimited-mailbox paid tier at $15 a month.

Verdict

Choose Mails.ai if you are a developer building transactional or conversational email into an agent workflow and want structured replies with injection scanning across every plan. Its free tier supports evaluation without a card, and paid tiers scale agent count and monthly volume. Look elsewhere if you need cold outreach, dedicated IP sending now, or compliance coverage that includes SOC 2 or HIPAA.