How to Check If an Email Address Exists (Without Sending)

You can't tell if an email exists just by looking at it. user@gmail.com looks valid — but it might not exist. CheckMail1 verifies whether the mailbox is real without sending any email.

Why Not Just Send a Test Email?

• Sending to invalid addresses raises your bounce rate
• High bounce rates damage your sender reputation
• Gmail and Outlook may block your domain if bounce rate exceeds 5%
• You'd need to wait for a bounce — not instant

How to Check If an Email Exists

The CheckMail1 API uses direct server-side verification — no email sent, results in under 2 seconds:

curl 'https://checkmail1.com/api/verify?email=user@example.com' \
  -H 'Authorization: Bearer YOUR_API_KEY'

# Response if email exists:
{{"valid": true, "reason": "deliverable"}}

# Response if email doesn't exist:
{{"valid": false, "reason": "mailbox_not_found"}}

Works for All Major Providers

Most tools can't check Gmail or iCloud — they return "unknown" because these providers block generic SMTP probing. CheckMail1 uses provider-specific logic to check these correctly.