MailSink vs MailSlurp: pricing, MCP, and BYOD compared

MailSlurp and MailSink both give you real disposable email inboxes for tests and AI agents. That puts them in a different bucket from Mailtrap (which is a sandbox for outbound email, see our Mailtrap comparison) and closer to each other.

This post shows where they differ so you can pick without guessing.

TL;DR

If you need custom domains today and volume pricing, MailSlurp still wins. If you want a lower bill, MCP integration, and are fine with shared domains for now, MailSink.

What MailSlurp does

MailSlurp has been around since 2019 and is a mature player. Key product surfaces:

• REST API for inbox provisioning, reading, sending.
• SMTP support for receiving at your own MTA.
• Webhooks for push-style delivery of new messages (MailSink does not have this in v1).
• AI transformers: pre-built processors that parse common senders.
• BYOD: paid plans let you attach a domain you own.

Pricing starts at $69/mo for Team tier and climbs through $149/mo and $249/mo. A free tier exists with 100 emails/month caps.

What MailSink does

MailSink ships a smaller surface and bets on being cheaper and agent-friendly:

• REST API for inbox provisioning, reading, and long-poll waits.
• MCP server for Claude Desktop, Claude Code, Cursor, and other MCP clients. First-class.
• OTP and verification-link extractors at ingest. No processing on your end.
• TTL-based retention: 1 hr free, 24 hrs Pro, 7 days Team. After TTL, messages are deleted from storage.

Pricing: $0 free (50 inboxes/mo, MCP included), $15 Pro (2,000 inboxes/mo, 600 req/min), $49 Team (20,000 inboxes/mo, 3,000 req/min).

Feature-by-feature

API ergonomics

Both expose REST. The shapes are similar enough that migrating tests is mostly a find-and-replace on endpoint paths and auth headers.

MailSink adds @mailsink/mcp as a first-class client. wait_for_email as a tool call is a big step up from polling endpoints when the driver is an LLM. MailSlurp has no MCP support as of April 2026.

Webhooks

MailSlurp has them. MailSink does not in v1 and relies on long-poll (wait-for-code blocks up to 60s). For most QA workflows the long-poll is enough; if you’re building async event-driven backends that need push, MailSlurp is the right fit today.

BYOD

MailSlurp supports custom domains on paid plans. You verify DNS, attach the domain, and inboxes on that domain behave like any other. If this is non-negotiable, MailSlurp wins.

MailSink has BYOD on the waitlist. Our current setup uses shared rotating domains (codenotify.net, letterhub.net, mailkite.net). Addresses look like [email protected]. Fine for most signup flows; not fine if you need a permanent customer-facing namespace.

Extraction quality

Both extract OTPs and verification links from common senders. MailSlurp calls their approach “AI transformers”; MailSink calls it “basic extraction” in docs because it’s pattern-based with per-sender tuning (Stripe, GitHub, Clerk, Supabase, Auth0, Google, Resend, AWS, and more). If a sender is not supported, both let you read the raw message body.

Pricing math

Run a rough CI example. A test suite that runs 300 signup flows per day across 30 devs, 5 days a week. That’s about 33,000 inboxes/month.

• MailSlurp: needs the $149/mo plan at that volume.
• MailSink: Team tier at $49/mo covers 20,000 inboxes. A single account hits the cap at roughly 20k; a second seat or Team plan adjustment handles the rest.

For the specific “a lot of CI flows” workload, MailSink is cheaper by $80-100/mo. For a BYOD scenario where you need a dedicated namespace, MailSlurp is still the right call at the moment.

When to pick MailSlurp

• You need bring-your-own-domain in production today.
• You want webhooks instead of long-poll.
• You run high-volume workflows and want one consolidated plan.
• You have existing SMTP infrastructure you want to plug into.

When to pick MailSink

• Price matters and you’re fine with shared domains.
• You’re driving tests or signups from Claude, Cursor, Claude Code, or another MCP client.
• Your workflow is bursty and TTL auto-cleanup keeps things tidy.
• You want to pay for what you use (flat plan tiers, no per-email pricing).

Migration notes

Swapping MailSlurp for MailSink in an existing test suite is mostly mechanical:

- const { MailSlurp } = require("mailslurp-client");
- const mailslurp = new MailSlurp({ apiKey: process.env.MAILSLURP_KEY });
- const inbox = await mailslurp.createInbox();
+ const r = await fetch("https://api.mailsink.dev/v1/inboxes", {
+   method: "POST",
+   headers: { Authorization: `Bearer ${process.env.MAILSINK_API_KEY}` },
+ });
+ const inbox = await r.json();

// sign up using inbox.address
// ...

- const email = await mailslurp.waitForLatestEmail(inbox.id, 30000);
+ const r2 = await fetch(
+   `https://api.mailsink.dev/v1/inboxes/${inbox.id}/wait-for-code`,
+   { headers: { Authorization: `Bearer ${process.env.MAILSINK_API_KEY}` } },
+ );
+ const { code } = await r2.json();

The MailSink API docs cover the full endpoint list; in practice you need three endpoints to migrate.

FAQ

Does MailSink have webhooks like MailSlurp?

Not in v1. Webhooks are on the roadmap. The long-poll endpoint (wait-for-code, up to 60s) covers most test scenarios.

Can I bring my own domain on MailSink?

Not yet. Join the waitlist to get notified when Pro-tier BYOD ships.

Does MailSlurp have an MCP server?

Not as of April 2026. MailSink’s package is @mailsink/mcp on npm.

How does MailSink handle bounce rates on shared domains?

Domains rotate across a reserve pool. When a sender flags one, new inboxes provision on a clean domain until the flagged one clears. Existing inboxes on the flagged domain keep receiving.

Can I use both?

Yes. Some teams run MailSink for AI-agent workflows (MCP-driven) and MailSlurp for webhook-heavy async pipelines.

Next

• Try MailSink free (50 inboxes/month)
• MCP server for AI agents
• MailSink vs Mailtrap (different category)
• MailSlurp pricing for their latest plans