Is there a way to allow email addresses which are external to your domain but defined as a contact in the Active Directory to directly send email via SMTP though our Exchange Online (Office 365) server.
We have a network of 30 outside (independent sales reps) who are defined as contacts in our Active Directory. They access or ERP system using this ID. However when they access a function in the ERP the application sends out an SMTP request to trigger an email using their non domain email address (eg John.firstname.lastname@example.org). Since it is coming from a non-domain computer and a non-domain email address it never gets sent. I do not want to open it up as an unsecured relay but I would like to accept relay requests from the external emails that are defined in the AD.
Can this be done?