I'm assuming that you're trying to do basic email forwarding instead of full synchronizing via UVM. Unfortunately, the MiVB can't send email using authentication, and all that you're left with is relay. The MiVB must be allowed to relay emails off O365 for it to work. I did some searching and it looks like it's possible to configure O365 to permit relaying. I'm not familiar with managing O365 so I can't help you there, but try searching for 'o365 email relay connector'.
An alternative is to setup a server in-house to relay emails. A box running basic MSL can work since it can be configured to use authentication when sending email, and to allow other devices to relay emails off it. Here's a summary of the steps:
1. Install MSL on to a computer (or ideally a virtual machine) and don't enter an ARID during the initial setup.
2. In MSL, go to Email Settings
a. Configure the SMTP server and credentials in "Server to use for outbound SMTP".
b. Set "SMTP email injection restrictions" to "Accept only from trusted networks".
c. If the MSL box is in a different subnet than the 3300, configure the 3300's subnet as a Trusted Network in the "Networks" section.
3. On the MiVB, follow the instructions to configure voicemail to email forwarding and use the MSL's IP address as the "Email Server" in "System Options".
If an email is sent successfully it will show up in the qmail logs on the MSL server. It does not show up in the MiVB's logs, but failed messages will. If your test message fails be sure to check the qmail logs. It is pretty good about giving clues as to why it's not working.
