A verified result means the mailbox existed and accepted mail when we checked it. Most verified addresses deliver. Occasionally one bounces anyway. Before you write to us, the bounce message usually tells you why.
Read the bounce message
Open the bounce (sometimes called a non-delivery report) and look for the reason:
| The message says something like | What it means |
|---|---|
"User unknown", "mailbox not found", "address does not exist", code 550 5.1.1 | The mailbox doesn't exist (any more). A real bounce |
| "Mailbox full", "over quota" | The mailbox exists but is full. Try again later |
| "Blocked", "spam", "policy", "reputation", "not authorised to send" | The receiving server refused your message, not the address. The address is fine |
"Temporary failure", codes starting with 4 | A temporary problem. Your sending tool usually retries |
Only the first kind means the verification is in question. Blocks and policy rejections are about the sending domain, its setup (SPF, DKIM, DMARC), its reputation or the content of the message.
Why a verified address can bounce
- It changed after the check. People leave companies and mailboxes are closed, sometimes within days. A result describes the moment of the check. The older it is, the more likely it has changed.
- A gateway answered for the mailbox. Some companies' security gateways accept checks and only reject mail later.
- The domain is catch-all. A catch-all address that wasn't resolved is not verified, and some of them bounce. Make sure you're looking at a verified result, not catch-all.
- The address was changed afterwards. A typo introduced when copying the address into your sending tool.
Lower the risk next time
- Verify close to sending. Re-check a list that's more than a few weeks old before a campaign. See Re-checks and the 180-day history.
- Resolve catch-alls instead of sending to them unverified. See Resolve catch-all addresses.
- Watch the deliverability index on strict domains. See The deliverability index.
- Look after your sending setup. Many "bounces" are blocks of the sender, not bad addresses.
Tell us about it
If the bounce says the mailbox doesn't exist and the address was verified recently, we want to know. Email support@filtrat.io with:
- the address;
- when you verified it, and in which job or list;
- when you sent to it;
- the full bounce message, including the error code (copy the text, or attach the bounce email).
We'll investigate what happened, especially if you believe a result was wrong because of a fault on our side.
Credits for results that were delivered as checked aren't refunded, because a verification describes the address at the time of the check. See the Terms for details.