MMS-enabled terminals on the market today are very complicated to use. It takes several steps to create a multi-slide MMS-message with images and text. This discourages users from using it. To increase usage of MMS, several companies provide web-based or stand-alone programs that allow users to create and send MMS-messages from a regular computer. However these editors have many limitations and are not user-friendly. This thesis describes the design and implementation of a user-friendly web-based MMS-portal where users can create, edit and send MMS-messages. The portal is integrated into Densitet’s system for development of mobile services. Conclusions that can be draw from this work are that problems with MMS interoperability have mostly the poor standardization to blame. Different terminals support different types of images and sound formats, and to make the MMS-portal user-friendly, format conversions of uploaded content had to be implemented. Also the MMS-portal only supports basic MMS-functionality. If the MMS-specification includes more audio and image formats and if the MMS-terminals are upgraded to handle these formats, sending MMS-messages will be easier and mobile messaging will continue to grow.