Why big lists take time

Who this is for: anyone verifying thousands of addresses who wonders why the progress bar moves slowly.

The short answer

Mailbox checks are paced on purpose. Mail servers watch for anyone asking about many mailboxes quickly, and they block or mislead fast checkers. Going slowly keeps the answers honest and keeps our checking servers trusted, which protects the accuracy of your results.

What is fast and what is slow

• Fast: the quick checks (format, typos, throwaway domains, domain lookups, shared inboxes). Addresses that fail here are done in moments.
• Paced: the real mailbox check with the receiving server, at about one check per second. Microsoft accounts (outlook.com, hotmail) are checked through Microsoft at a similar, slightly slower pace.
• No wait: Yahoo and AOL addresses are marked Risky without a mailbox check.

How long to expect

Roughly, for addresses that need the mailbox check:

Lists with many invalid or Yahoo addresses finish sooner. When a receiving server asks us to slow down, every check waits a little, so a run can take longer at busy times. Addresses whose check could not finish get a second try at the end of the run, which adds a few minutes.

You do not have to wait

• Leave the page. The run continues on our servers. Come back to the Email verifier or the list to see the progress (1,250 of 5,000 checked).
• Results appear as they come. The counts under the progress bar grow during the run.
• Stop any time. Leads already checked keep their result.

Tip: Upload big lists with Verify these emails after import ticked the day before your campaign starts. The results are ready when you are.

Common mistakes

• Starting a campaign on a list that is still being checked. Leads not checked yet count as Not verified. A campaign that leaves out Not verified may leave out those leads. Let the run finish first.
• Starting the same list again and again. Only one run per list can be active. Let it finish.

Next step

Put it all together: Keep your bounce rate low.