By default, DIME/ WSE 2.0 doesn't allow adding/sending attachments larger than 4096 KB of size. If you intend to send larger files, which are over the 4 MB limit (including the SOAP message), you need to add some tags to the web.config file of the service as well as, remember, of the receiver (client) end. You need to add values to override the values of the maxRequestLengths.

 http://www.codeproject.com/soap/DimeTest.asp?df=100&forumid=121647&exp=0&select=1631445

 By the way, moving to MTOM is fairly easy, and I would suggest it as DIME is no longer supported in WSE 3.0.

Thanks a lot. Can u tell me how to upload and download mutliple files encoded with MTOM.