Could "To: " or "Cc: " or "Reply-To: " be the last field in the header of an email

[Habib Abassi]

Hi,

If anyone has an answer for this question :

        Could "To: " or "Cc: " or "Reply-To: " be the last field in the header of an 
email ?

What about the order of the field in the header ?

Thanks.