Hey YC

I’m Amine, CTO of Mailwarm (YC S20) and today we’re launching mailX.
Thami is the CEO, Othman is our Head of deliverability and we are ready to help you with all your email deliverability problems.

We’ve been working on email deliverability since 2020. Mailwarm started as an email warmup tool and became #1 Product of the Day on Product Hunt. Since then, we’ve helped thousands of teams improve sender reputation and inbox placement.

Today, we’re building a broader email deliverability ecosystem:

• Mailwarm helps teams build sender reputation through real inbox interactions.
• mailX helps humans and AI agents diagnose deliverability issues.
• MailAdept helps companies fix and monitor deliverability continuously with AI agents and human experts.

Today we’re launching mailX.

TL;DR

mailX tells you why your emails go to spam and how to fix it.
You can run a deliverability check from the web, use it through a JSON API, or plug it directly into AI agents through MCP.

No signup.
No API key.
Free to use.

Try it here: https://themailx.com
MCP endpoint: https://themailx.com/mcp

You can also book a call with one of our email deliverability expert HERE.

🚨 The Problem

Email deliverability is technical, your marketing team can’t handle it.

Email is still one of the most important growth channels for startups.

Founders use it for cold outreach.
Sales teams use it for outbound.
Marketing teams use it for campaigns.
Products use it for onboarding, activation, and transactional emails.

But when emails start going to spam, most teams don’t really know why.

They check random tools.
They look at raw DNS records.
They ask ChatGPT.
They change things blindly.
They wait and hope inbox placement improves.

The problem is not only that deliverability is technical.

The real problem is that most tools show data, but don’t explain what matters or what to fix.

And now, with AI agents sending emails, monitoring systems, and managing workflows, this problem gets bigger.

Agents need access to live deliverability tools too.

💡Our Solution

mailX is a free deliverability diagnostic platform for humans and AI agents.

With mailX, you can analyze a domain in seconds and get a clear report showing:

• What is working
• What is broken
• Why it matters
• What to fix next

The web app gives founders, marketers, sales teams, and developers a simple way to understand why emails may go to spam.

The API and MCP server make the same tools available to AI agents and developer workflows.

So instead of copying DNS records into different tools, your agent can directly check email authentication, blacklist status, mail server configuration, and deliverability signals.

⏳How it works

1. Enter a domain on themailx.com
2. mailX runs a live deliverability audit
3. You get clear issues, explanations, and fixes
4. Developers can use the JSON API
5. AI agents can use the MCP endpoint directly

The best part is that you can lets you AI Agent fix your deliverability or directly integrate it to your Claude or ChatGPT.

Here’s a quick demo of mailX:
https://www.youtube.com/watch?v=YWmV7-wthQI

In the demo, we show:

• Running a domain audit
• Getting clear fixes
• Using the MCP/API layer for AI agents and developers

We currently support checks and tools for email authentication, DNS records, blacklist status, mail server configuration, and record generation.

Why now?

Email deliverability used to be something only email experts cared about.

Today, every startup relying on outbound, lifecycle emails, AI SDRs, or automated email workflows needs to understand it.

At the same time, AI agents are becoming part of the stack.

But agents need tools.
They need live data.
They need safe, structured ways to diagnose and act.

That’s why we made mailX available through:

• Web app
• JSON API
• MCP server
• Agent skill
• LLM discovery endpoints

Our belief is simple:

Email deliverability should be understandable for humans and usable by AI agents.

Backstory

In 2019, we failed a startup after 2 years of work.

After that, we decided to test ideas much faster: one launch per week.

Every launch used the same growth channel: email.

Cold emails.
Partnership emails.
Launch emails.
Follow-ups.

That’s when we understood something obvious: If your emails don’t land in the inbox, nothing else matters.

That led us to build Mailwarm in 2020.

After years helping thousands of teams improve deliverability, we kept seeing the same pattern: People don’t know why they land in spam.
And even when they see the data, they don’t know what to fix.

mailX is our answer to that.

🙏 Our Ask

We’d love your feedback from the YC community.

If you are doing cold email, email marketing, transactional email, or building AI agents that send or monitor emails, try mailX and tell us what is missing.

Also, if you are building an AI agent or workflow where email deliverability matters, we’d love to talk.

Try mailX: https://themailx.com
Book a call through MailAdept if you want help choosing the right setup: https://calendly.com/mailwarmsessions/mailx