How to prevent marketo form submit with personal email id

Unfortunately, the code in that post is incorrect. It doesn't properly search case-insensitively for the domains and only on the right-hand-side of the email address.

You should use the code in this CodePen instead: MktoForms2 :: Multiple Email fields w/questionable validation (prefix only)

However, note that all such attempts are prone to false positives if you don't deliberately add every single (full) domain. For example, user@live.example.io will be blocked if you only look for the word "live" at the beginning of the domain. Same with user@outlook.example.corp  which could be a corporate Exchange server, not personal email.

Note