Is it possible to check an email header ('To Header' contains 'name') ? But not on account level (mail filter). Because I want to check incoming mail, if the To header contains a name from an employee who doesn't work in the company anymore. So the email account doesn't exist.

So the filter:

To header contains employee@company.com(account doesn't exist)
then
copy message to 'account that exist' and auto reply 'i don't work here anymore'...