Is the volunteer organization who owns Exchange server? And those personal accounts are external to Exchange organization?
If so, I have two methods:
1 Create mail contacts for the volunteers' personal accounts.
Then create a transport rule that when message is arriving an internal mailbox, send an incident report to the mail contact, here is an example:
You might want the relation to be one-to-one, or several-to-one, tell me if you need further assistance.
2 Configure Outlook script rule, follow the guidance in this:
Outlook's Rules and Alerts: Run a Script
Run a Script Rule: Send a New Message when a Message Arrives
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