Punchh uses standard regex to validate the email address format as entered by users in the app.
Here is the regex for reference - /^(([^<>()\[\]\\.,;:\s@"]+(\.[^<>()\[\]\\.,;:\s@"]+)*)|(".+"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/
Also, Punchh does not use any max character limit on email validation.
If further assistance is required, submit a ticket to Punchh Support. (For help submitting a ticket, click here)