Yes, this should be possible. You can take a look on the app store. There is demo app to handel REST services.
Calling (SOAP) web services from Mendix using MTOM is supported for sure, but last time I checked publishing them was not.
Not entirely sure if this was later added in a more recent version of Mendix, but I don’t think so.
Could you share the info of how it is possible to send the attachments as MTOM via REST?
Thanks in advance,
Yes. Its possible. Since input parameters of published SOAP service supports only primitive data types (String, Integer,...). So you need to encode the document into base64 string before sending a request. While receiving just decode the base64 string and import the file.