It looks like it is possible - although I need to check the full API:
Variable: You can map a string from the email subject, body, header, or sender's email address. To do this, use one of the following keywords: %SUBJECT%, %BODY%, %HEADER%, or %SENDER%. For example, if you use %SUBJECT%, the email subject content is used as the input parameter. To pick up attachments, enter a file pattern that the email endpoint can use to select the attached documents. For example, entering
*.pdf selects any attached document that has a .pdf file name extension,
* selects any attached document, and
example.pdf selects any attached document named example.pdf.