Attachments smaller than 768 bytes, when submitted from a .NET web service to Service Manager, are base64 encoded and inserted into the SOAP message. MTOM handles larger attachments using MIME parts.
When Service Manager receives the smaller attachments, they are attached with no content because SM doesn't look for the content in the SOAP message.
We ask that Service Manager be updated to also be able to read the SOAP message for attachment content.
The following links to articles provide more background to the issue:
....."At this time, binary data smaller than 768 bytes is base64 encoded and inserted into the SOAP message ... Otherwise, MTOM uses MIME parts to send the data...."