Hi Neal,
Thanks for reaching out! I unfortunately couldn't replicate this issue. I just added two entries to Sender Priority, and they are both preserved after refreshing the site, logging out and back in, clearing the browser cache and logging in with a different browser. I'll keep these entries configured and check back in tomorrow to see if they're still there.
For additional troubleshooting... Did any service restarts take place on the server or in IIS? Had you upgraded SmarterMail after adding the priorities? Finally, if you right-click on the preview pane and open the browser developer tools, do you see any errors on the Console tab?
Thank you!
Andrea Free
SmarterTools Inc.
877-357-6278
www.smartertools.com