Dead Simple Email sells many inboxes at a flat price. MCPmailer sells conversations your agents hold and you can supervise, over MCP.
Agent inbox APIs · Dead Simple Email claims checked July 2026
Dead Simple Email creates inboxes, sends and receives, and posts real-time webhooks, aimed squarely at people tired of Gmail suspensions and per-seat pricing. Its headline is the unit economics: on the order of a hundred inboxes for a flat monthly fee.
If you need a large number of low-traffic inboxes at a predictable price, for catching signup confirmations or fanning out test accounts, flat-rate inbox pricing is the cheapest way there and we are not competitive on it.
We are priced and built for a handful of agents holding real conversations with real people under your domain, where thread history, sending reputation, and the audit trail matter more than how many addresses you can hold at once.
Counting inboxes optimises for breadth: many addresses, little traffic, no relationship. Counting conversations optimises for depth, which is where the hard parts live: threading, reply-first quotas, a searchable history, and a human who can read it.
Verify agents.yourcompany.com and your DKIM signs with your own domain, on a sending pool separated by trust tier. Many-cheap-inbox products necessarily share a managed domain across everyone using it, which is fine for receiving and a real risk for sending anything that matters.
Contacts with per-contact memory, notes, an encrypted vault, a public tunnel hostname per agent, mail rules with whitelist mode. An agent that can only send and receive is a script; the rest is what makes it useful without you re-supplying context every run.
Every row is a claim we could defend with their documentation open beside it. Where they are ahead, the row says so.
These products barely overlap, so be honest about which side of the line you are on.
Many disposable addresses
Stay where you are. Paying per conversation for inboxes that receive one confirmation email each makes no sense.
A few agents talking to customers
Come over. You are buying threading, reply-first quotas, your own domain reputation, and oversight, not address count.
Both at once
Common and reasonable: cheap inboxes for machine-to-machine signup noise, ours for the agent that talks to humans.
For many low-traffic inboxes, flat inbox pricing wins outright; their published entry point is around $29 a month for roughly a hundred inboxes. For a few agents sending real volume from your own domain, our base plus usage ladder is usually less, and the free tier covers 3,000 emails a month.
Yes, but you pay per inbox above your plan's allowance, so it is the wrong tool for a hundred addresses that each receive one message.
Yes. Verify a subdomain and your mail is DKIM-signed as you, on a pool separated by trust tier rather than shared with every free account.
This one, and not because of the tooling: a customer-facing agent needs a sending domain whose reputation you control, thread continuity over months, and a human able to read what was said. Flat-rate inbox products are optimised for the opposite case.
If you are choosing between agent inbox APIs, the deciding question is usually where the conversation state lives. Ours lives in the mailbox, and your agent reaches it with tools instead of with a schema you maintain.
The free tier is 3,000 emails a month across three agent inboxes, no card, with receiving, threading, and search included. Enough to watch a real conversation happen before you decide.
More Agent inbox APIs