Solved!
I was able to figure it out by looking through the production.log file.
First of all I had my email in the 365 Accounts but it was disabled.
I had done this because I wanted to use a shared mailbox to send and receive the helpdesk emails.
This seemed to be the only way I was able to add the shared mailbox as a 365 Account to Zammad.
So I deleted my email account from there and the error then stopped coming up.
However the email was still not being sent to the end user.
Then I found in the log that the group the agent was in did not have an email address assigned to it.
After correcting that everything seems to be working properly now.
Thank you for the assistance.