To enable you to maximize your email authentication opportunities,you can now specify the MAIL FROM domain of emails you send with Amazon SES. The MAIL FROM address, also called the "envelope MAIL FROM, or " is the address that the sending mail server (Amazon SES) specifies to a receiving mail server to indicate the source of the message. Whereas you beget always been able to specify the address that recipients see in their inboxes (the "From" address from the email header),this is the first time that Amazon SES enables you to specify the MAIL FROM domain.
Source: amazon.com