The address is not written in a valid format, so the server will not accept it.
Hard bounce · permanent
Common causes
- Spaces or invalid characters in the address
- Missing @ or domain part
- Copy-paste artefacts such as < > or trailing dots
How to fix it
- Clean the address and remove invalid characters
- Validate addresses at sign-up so bad syntax never enters your list
Inbox CheckerRun the right check for your domain or paste the full bounce message for a precise explanation.
Open Inbox Checker →Frequently asked questions
How do I validate email syntax?
Email verification checks syntax first, then the domain and the mailbox.