Common causes
- A typo in the name or in the domain, such as gmial.com.
- The person left and the company deleted the mailbox.
- The address was guessed from a pattern and never existed.
- An old list entry for an account that has since been closed.
How to fix it
- Take the address off your list and stop sending to it.
- Compare it with the original source; a single wrong letter is common.
- Read the full bounce text: servers often repeat the exact address they rejected.
- Check the rest of the list the same way before your next campaign.
How to prevent it Take the address off your list and verify the rest before the next send.
Frequently asked questions
Will this error go away if I try again?
No. A 5 at the start of the code means permanent. Mailbox providers expect you to stop mailing an address after this answer.
How does Mailcut report it?
Addresses that return this answer are marked Invalid with the reason "mailbox does not exist", so you can remove them from the report in one filter.