CheckMXSandbox
Free email checks + AI connector.
$0 forever
- Free Sandbox · Outbound runs on Starter
- Comes with email checks, free
Cold email that only lands on real inboxes.
Campaigns, sequences, warm-up and one inbox for every reply. Bring your own mailboxes and build your outbound workflow in one workspace.
Every plan comes with email checks, free.
A clearer signal before you send
Try a free email check.
Check an address before you reach out. Get a verdict and a reason. SMTP acceptance is a signal, not a delivery or inbox placement guarantee.
Free email check
Free
Syntax, MX, SMTP and catch-all checks, with context.
Works with the accounts and assistants you use
- Gmail
- Outlook
- SMTP / IMAP
- Claude MCP
- ChatGPT MCP
Campaigns & sequences
A thoughtful follow-up starts here.
Build multi-step campaigns, set your sending windows and keep every follow-up in order. Explore A/B testing on Growth and above.
Start your 14-day trial
Your mailboxes
Your accounts. One place to send.
Connect your own Gmail, Outlook or SMTP/IMAP accounts. Starter includes 25 connected mailboxes; Growth and Scale include unlimited connected mailboxes. CheckMX never provides mailboxes.
Start your 14-day trial
Warm-up
Give each mailbox time to find its rhythm.
Ramp up gradually, review mailbox health and keep an eye on daily sending caps. Warm-up is included on every paid plan.
Start your 14-day trial
Unified inbox
Every reply, back in the conversation.
Bring replies from your connected mailboxes together. See the intent, find the campaign and pick up where the conversation left off.
Start your 14-day trial
Take a closer look
From your first check to the next reply.
Real dashboard screens, filled with a fictional workspace. Names, companies and numbers are example data.
See the wider picture
Track sends, deliveries, bounces, replies and meeting requests from your send ledger. Opens are not tracked.
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Example data · Explore reports, campaigns, replies and email checks.
AI assistants
Your numbers, right inside your AI assistant.
Connect CheckMX to Claude, ChatGPT or Cursor through MCP. Explore the real card below: switch views, change the date range and pick a chart type.
Your assistantExample data
How are my campaigns doing this week?
Interactive example data. Connect your own workspace to see your results.
Simple pricing, checks included.
Every plan comes with email checks, free.
Starter
Free during betaFind your rhythm. Start more conversations.
$0 $37/mo · later $37/mo
- 6,000 emails sent/mo
- 15,000 contacts
- 25 connected mailboxes
- Comes with email checks, free
Growth
Coming soonMore reach. Room to experiment.
$87/mo
- 150,000 emails sent/mo
- 300,000 contacts
- Unlimited connected mailboxes
- Comes with email checks, free
Scale
Coming soonSerious volume. A personal touch.
$297/mo
- 500,000 emails sent/mo
- 1,000,000 contacts
- Unlimited connected mailboxes
- Comes with email checks, free
CheckMX is free during beta, no card required. Compare plans →
A little more clarity
Frequently asked questions
The details, before you hit send.
What does “deliverable” actually mean?
The destination mail server accepted the recipient during an SMTP probe. That is a useful signal that a mailbox accepts mail, but it does not guarantee that your message will arrive in the inbox.
How do you handle catch-all domains?
We check whether the domain accepts a random address. If it accepts any recipient, we label the result risky: acceptance alone cannot prove that a particular inbox exists.
What happens when a result is unknown?
When SMTP cannot finish because of a timeout, deferral, or blocked connection, the result stays unknown. Unknown results are left unconfirmed.
Can I verify a whole list?
Upload a CSV up to 2 MB, with up to 10,000 unique addresses per job. Split larger lists into several jobs. Review the estimated duration before starting; remaining time updates as checks finish. Each address gets its own verdict and reason, so you can review deliverable, risky, undeliverable, and unknown results.
Are email checks included?
Yes. Every plan, including the free Sandbox, comes with email checks at no extra cost. CheckMX is free during beta, no card required. See the plans on the pricing page.