How to sent a mail or work item to SAP inbox with attachment?

Dear experts,

I'm not talking about sending to external mail which would require SMTP configurations, I'm asking about sending main to SAP inbox.

I've tried to follow some tutorials to attach any file in a mail or a work item to be sent to a user on the system.

like this one Sending multiple attachment in user decision step of workflow

and here is another discussion with same question:Sending email to SAP inbox with attachment

Yet I couldn't be able to achieve the requirement.

It would be highly appreciated if some one could guide me on how to send a mail or a work item to SAP inbox with ANY kind of attachment?

Thanks in advance,

Omar El Halawany