Office 365 and voicemail to email relay - problem is that the voicemail system is old and does not support TLS and the gotcha is you cannot setup a "user" that actually sends the email.
I've setup a simple IIS6 smtp relay on a server 2008/2012 to relay email from a copier/MFP device to O365. In the copier, I can set a "Sender" and then alias that to the authenticated email on the backend and it works to Office 365.
In this case the voicemail system is so old that each user that get voicemail to email has their own email address listed in the voicemail system. I cannot add all these users to the IIS SMTP server so not sure the best way to accomplish.
Would direct send work? Do I create a connector on the Office 365 system and have the voicemail system send to the MX record?
Any suggestions would be great and thanks.