This thread may be able to help you (https://jamfnation.jamfsoftware.com/discussion.html?id=11470). It discusses changing an email address. Personally, I'd use AppleScript to delete the old account and just add the new one...
-t-
Here is a script we used in our environment via Self Service when migrating some users from an acquisition to our mail server. Super simple (just remove the autodiscover stuff if you don't need it):
#!/usr/bin/env bash
userPID=`ps -ef | grep "loginwindow console" | grep -v grep | awk '{print $2}'`
useris=$(ls -l /dev/console | awk -F"1 " '{print $2}' | awk -F" " '{print $1}')
launchctl bsexec $userPID su "$useris" -c /usr/bin/osascript <<HOOK
tell application "Microsoft Outlook"
set the server of every exchange account to "https://yourserveraddress"
end tell
tell application "Microsoft Outlook"
set background autodiscover of every exchange account to false
end tell
display dialog "Email Server Address Fixed" buttons {"OK"}
HOOK
@chriscollins Thank you! This is perfect!