MailSlurp is built for email testing and automation. MCPmailer is built for production agents talking to your customers.
Agent inbox APIs · MailSlurp claims checked July 2026
MailSlurp gives you disposable inboxes over an API, unlimited on higher plans, plus SMS numbers, and has spent years serving QA suites that need to receive a confirmation mail and assert on its contents. Its wait-for-latest-email endpoints are excellent at exactly that.
For test automation it is the obvious pick and we are not trying to replace it. If CI needs to spin up an inbox, wait for a signup email, pull a code out of it, and throw the inbox away, use MailSlurp and never think about it again.
Test inboxes and production inboxes have opposite requirements. A test inbox is disposable and its reputation is irrelevant. A customer-facing agent needs a warm sending domain, DKIM on a subdomain you own, thread continuity across months, and a human who can read what was said.
A testing platform sends little and cares less, because nothing it sends has to land in a stranger's inbox. We isolate senders by trust tier, run per-tenant configuration sets so one bad account cannot poison yours, and enforce a suppression list before every send. That machinery only exists if production mail is the point.
MailSlurp's waiting primitives are built to satisfy a test: give me the latest message matching this. Ours are built to continue a conversation: wait_for_reply takes a thread_id, get_thread returns the exchange in order, and In-Reply-To linkage survives clients that rewrite headers.
Disposable inboxes are, by design, disposable. Our free tier keeps 30 days and paid keeps history indefinitely, because an agent that answers a customer in March may need what was agreed in January, and so may your lawyer.
Every row is a claim we could defend with their documentation open beside it. Where they are ahead, the row says so.
Most teams that adopt us keep MailSlurp. They are solving different halves of the same word.
Keep MailSlurp in CI
Signup flows, magic links, and end-to-end assertions. Nothing here is better at that.
Move the agent to its own address
Anything a real person will read, reply to, or complain about belongs on a domain you own.
Point staging at a sandbox
So a half-finished agent cannot email a customer while you are still iterating on the prompt.
You can, and people do. You inherit a shared testing-oriented sending reputation, disposable-by-default retention, and you build supervision and cold-send controls yourself.
Not especially. There is no sandbox mode and no throwaway inbox concept. Use MailSlurp or Mailtrap for that and keep us for mail that reaches real people.
No. Email, contacts, notes, vault, and tunnels. If you need SMS in the same product, MailSlurp covers both.
30 days on the free tier, indefinitely on paid plans, with the raw MIME retained so a thread can always be reconstructed.
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