HTTP/1.1 uses many of the constructs defined for Internet Mail (RFC 822) and the Multipurpose Internet Mail Extensions (MIME ) to allow entities to be transmitted in an open variety of representations and with extensible mechanisms. However, MIME  discusses mail, and HTTP has a few features that are different from those described in MIME. These differences were carefully chosen to optimize performance over binary connections, to allow greater freedom in the use of new media types, to make date comparisons easier, and to acknowledge the practice of some early HTTP servers and clients.
This appendix describes specific areas where HTTP differs from MIME. Proxies and gateways to strict MIME environments SHOULD be aware of these differences and provide the appropriate conversions where necessary. Proxies and gateways from MIME environments to HTTP also need to be aware of the differences because some conversions may be required.