Why Is My Verification Taking a Long Time?

Most single verifications complete in under 10 seconds, and bulk jobs process at high speed. However, some verifications take longer due to how remote mail servers respond.

Common Reasons for Delays

Greylisting

Some mail servers use greylisting as a spam prevention technique. When a new sender connects, the server temporarily rejects the request (450/451 response) and expects the sender to retry later. Mailthentic handles this automatically by retrying up to 3 times with increasing delays (30, 60, and 120 seconds).

A single email verification against a greylisting server can take up to 5 minutes.

Slow Mail Servers

Some mail servers respond slowly due to:

• High load or poor infrastructure.
• Geographic distance (servers in remote locations).
• Intentional delays to deter automated probing.

Large Bulk Jobs

Bulk jobs process emails in batches with built-in rate limiting to avoid overwhelming mail servers. A list of 10,000 emails typically takes several minutes to complete. Very large lists may take longer.

Domain-Level Throttling

To protect our sender reputation and respect mail server limits, Mailthentic throttles verifications per domain. If your list has thousands of addresses at the same domain, they'll be processed over time rather than all at once.

What You Can Do

• For bulk jobs: Close the browser and come back later. Your job runs in the background.
• For single verifications: Wait for the result — the page auto-refreshes. If it times out, the result will show as "unknown" and you can retry later.