Microsoft announced a change in July 2020 about changing the default outbound mail policy to no longer allow automatic forwarding to external recipients. This affects both the mailbox-level policy auto-forwarding as well as individual inbox rules.
Questions
Why was this change made?
Automated external email forwarding is a tactic attackers use to exfiltrate data out of an organization. To counter that, Microsoft is updating the default outbound anti-spam policy to prevent forwarding to external recipients.
Who does this affect?
This change affects anyone using Office 365 email that currently has an auto-forwarder or inbox rule configured to forward to an external (non-Elon) address.
What will happen to the auto-forwarding rules I have in place now?
Any auto-forwarding rules on mailboxes will cease to function after September 01, 2020. Senders to these mailboxes will receive a non-delivery notification if their messages match a forward rule to an external (non-Elon) address.
Does this affect sending/receiving from students in Gmail?
Students with primary email in Gmail are not affected by this change.
Can I setup forwarders to Elon addresses?
Yes. This will remain unaffected. You may still auto-forward to an individual, shared mailbox, distribution group, or listserv if you so choose as long as it is managed by Elon.
Can I create an inbox rule to forward to a personal account?
No. This is not permitted. While Outlook/OWA will not expressly prohibit the creation of a forwarding rule to an external recipient, the rule will not function. Furthermore, IT staff will routinely follow up on external forwarding rule creation as part of a standard information security response.