Troubleshooting Outlook Email Agent Draft Reply Errors

Hey everyone! Hoping somebody can help me with this. I've created an email agent for Outlook that drafts automatic replies to specific customer requests. I started by testing on a "test" email account. On the test account, I was having the agent automatically reply (as opposed to creating drafts). When I switched the agent node function from "Send Reply" to "Create Draft Reply" and tested, I started receiving the attached error. I realize this error is pointing to a mailbox error, but it seems odd that the first time I ever received it (after testing for weeks) was when I switched to "Create Draft Reply." I've also now tested on a separate email from the same organization and I'm receiving the same error. Any help is appreciated!!! Alon J.