'From e-mail' field in workflow not respected

[Guido1982]

This is a custom workflow task from PDFMaker, so maybe there is an issue there. They've copied the stock e-mail task and all the variables. Now when I set an e-mail address in the 'From' field, the e-mails still get sent with the e-mail address that is set globally in the outgoing mail server settings in the 'From' header. Is this expected behavior? Any way to change it?