Attio requires that emails are in a valid format. If the email address is not valid, Attio will reject the email and the record cannot be imported
Please make sure that:
The email is a string referencing an internet email address
e.g. "help@attio.com"
See here for attio guidelines: https://attio.com/help/reference/imports-exports/migrate-data-from-another-crm#check-formatting