A Simple Object Access Protocol (SOAP) request can use HTTP's POST verb. In fact, however, the protocol requires that the first request to a server is made using M-POST. M-POST is a new HTTP verb defined using the HTTP Extension Framework (http://www.w3.org/Protocols/HTTP/ietf-http-ext ). If a request made using M-POST fails, the client can try again using a standard POST request. (In this case, future requests can also use POST because the server obviously doesn't support M-POST.) M-POST allows sending HTTP headers that can't be sent via the standard POST verb, providing more flexibility for SOAP users. Firewalls can even force the use of M- POST if desired, by simply refusing all HTTP POSTs with a content type of "text/xml-SOAP".