Check that the email has one `@` symbol
Check that there is text before and after the `@`
Check that the domain name has a valid format
Check that the domain contains at least one dot
Check that there are no spaces in the email address
Check that there are no invalid characters
Use an email validation regex
Send a confirmation or verification email
Check the domain’s MX records
Use an email validation API
Try a syntax check with a validation tool
Confirm the mailbox exists if possible