Currently IBM SmartCloud SMTP Servers cannot be used as a relay server to send mails from customer environment to internet.
e.g.- If customer is having certain applications then we cannot use IBM SmartCloud server as relay server to send mails to internet. The typical problem which arises is, it is restricted to accept mails only from the user's own internet address. This means applications using their own internet address in "From" address will not be allowed to send mails to SmartCloud server even if you provide correct user credentials. This restriction is in place to prevent using fake addresses (address spoofing) from IBM SmartCloud servers and user accounts. IBM SmartCloud only supports accepting SMTP mails from user clients like Outlook, Thunderbird. or any other IMAP/SMTP Client. IBM SmartCloud server does not support accepting mails from other applications or servers with their own "From" addresses. So there is a feature request to allow IBM SmartCloud servers as relay servers for sending mails to internet.