Guide
Passed, Failed, and Unknown email verification results explained.
Every MailGuard result falls into one of three categories. Here's what each one means and what to do with it.
No monthly subscription · Credits never expire · Unknown results use no credits
Passed
The address has valid syntax, the domain accepts mail, and the mailbox responded positively. Keep these. One credit is used.
Failed
The address has a syntax error, the domain doesn't exist, the mailbox doesn't exist, or the mailbox is full or disabled. Remove or suppress these. One credit is used.
Unknown
The server didn't confirm or deny the mailbox. Common causes are catch-all domains, temporary server errors, and greylisting. No credit is used.
Unknown doesn't mean bad. It means the check was inconclusive. Use what you know about where the contact came from to decide.
Reading the details column
The details column explains why an address got its status, such as 'passed all tests', 'role account', 'mailbox full', or 'blacklisted domain'. Use it to make finer decisions than the status alone allows.
What MailGuard can help with
- Checking single addresses or bulk CSV/TXT lists before a campaign
- Sorting each address into Passed, Failed, or Unknown, with a plain-language reason
- Flagging disposable domains, role accounts, syntax issues, and catch-all behavior
- Exporting a filtered list that contains only the results you choose
- Paying only for Passed and Failed results, since Unknown results use no credits
Limitations
Verification reduces uncertainty before sending. It does not guarantee inbox placement and does not replace consent or list hygiene.
Frequently asked questions
Why don't Unknown results use credits?
Because you didn't get a definitive answer. You pay only for Passed and Failed results.
Can I re-check Unknown addresses?
Yes. Temporary errors sometimes clear on a later check.
Related
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Pay only for Passed and Failed results. Credits never expire.
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