Enhancement adding extra attachements to emails from Request for Quotation output

[joos]

We are using Fiori tile Manage RFQ's to create request for quotations for suppliers. In these RFQ's we add attachments (drawings and other specifications).

With standard SAP we are able to send mail output from the Fiori tile but we cannot add the additional attachments to the output .

Now we would like to build custom functionality to add the attachment but we cannot figure out in where to do this. As the sending of the mail output is triggered via the Fiori tile we are not able to debug and find the correct  place or program to add our custom enhancements.