Multimedia Message Service (MMS), is a store-and-forward method of transmitting graphics, video clips, sound files and short text messages over wireless networks using the WAP protocol. Carriers deploy special servers, dubbed MMS Centers (MMSCs) to implement the offerings on their systems. MMS also supports e-mail addressing, so the device can send e-mails directly to an e-mail address. The most common use of MMS is for communication between mobile phones.
Although MMS looks to the user like e-mail; it is based on the concept of multimedia messaging. The presentation of the message is coded into the presentation file so that the images, sounds and text are displayed in a predetermined order as one singular message. MMS does not support attachments as e-mail does since all of the contents (text, photos, sounds and videos) are "in-line"; but to the end user it appears just like attachments to an e-mail.
WP-MMS is a special purpose MMSC which is not currently designed to forward messages as a normal MMSC would but rather post them into WordPress.