Maybe the SMTP-server blocks e-mails send to external e-mail addresses. Please check these settings first.
StijnGabriels-Oracle Thanks for the reply!
I in no way claim to be an expert when it comes to these things, but I doubt it is to do with email settings. Without going into too much detail about the structure of my Organisation, the company we outsource to is essentially a subsidiary of my organisation and utilise the same networks/settings, so if one side of the organisation is able to receive emails from OBIEE the other should be able to as well. I imagine it is more likely something that is incorrectly set up within OBIEE but I am unable to locate anything other than the "Device Options" menu