550 5.7.1 Client does not have permissions to send as this sender
I've setup an SMTP relay for Office 365. However I cannot seem to send any mails. I've done a search on this forums and other posts suggect that there needs to be a valid entry in the FROM field (an address with a send as permission). I am trying to send using my own account to others on the same domain.
I will be using the SMTP relay address on a printer and there is no FROM field on the printer. Can I pass this from within the IIS SMTP relay server somehow? Has anyone come across this problem?