1. Put it in one file
Export the list from your email tool, shop or CRM as a CSV, or copy the addresses into a text file, one per line. Other columns can stay; only the address is checked.
2. Remove duplicates
The same person often appears twice, sometimes with different capital letters. Anna@Example.com and anna@example.com are one mailbox. BounceTest counts and checks an address once, however often it appears.
3. Fix the obvious typing slips
Addresses typed into a form by hand carry slips: gmail.con, gamil.com, outlok.com. A good check points these out and suggests the domain the person meant. Correct the clear ones, and check them again afterward: the fixed address still has to exist.
4. Take out throwaway addresses
Temporary mailboxes that work for ten minutes are of no use on a mailing list. They are recognized by their domain, without asking any mail server. More in what a disposable email address is.
5. Verify what is left
Verification asks each address's mail server whether the mailbox exists, and stops before any message is sent. Every address comes back as one of a few results:
- Valid: the mailbox exists.
- Invalid: it does not; a message would bounce.
- Risky: the server accepts every address, or the mailbox is full, so a message may bounce.
- Unknown: the server did not answer this time.
What happens behind those words is described in how email verification works.
6. Remove the invalid ones for good
Delete them from the list, and keep them in a separate "do not import" file. Otherwise the next export from your shop brings them straight back.
7. Decide about risky and unknown
- Risky addresses from people who signed up with you themselves are usually real. Send to them in a small batch first and remove whatever bounces. Risky addresses from a list you did not collect are best left out. More in what a catch-all email address is.
- Unknown addresses are worth a second check a little later. A server that said "not now" often answers the next time.
Keeping it clean
- Confirm new sign-ups with an email that has to be clicked. It keeps typos and fake addresses out from the start.
- Remove hard bounces after every send. See why emails bounce for which ones are final.
- Check again before mailing a list that has been resting. A list that was clean a year ago is not clean now.
- Check each import before it joins the main list.
How BounceTest fits in
Upload the file or paste the addresses, and watch the list being checked: how far along it is, how long is left, and how the answers are turning out. When it is done, download only the valid addresses, the valid and risky ones together, or only the invalid ones for your records. A list can hold up to 100,000 addresses, and no email is sent to any of them.