Outlook web add-in traps

Posted on Jun 30, 2024 By Jason Liu

1. Cache of the Outlook add-in needs to be cleared before any update of it can apply
   • Reinstall the add-in
   • for /d %d in ("%LOCALAPPDATA%\Microsoft\Office\16.0\Wef\*") do @rmdir /s /q "%d"
   • del /s /f /q /a:h %LOCALAPPDATA%\Packages\Microsoft.Win32WebViewHost_cw5n1h2txyewy\AC\#!123\INetCache\*
   • rmdir /s /q %userprofile%\AppData\Local\Microsoft\Outlook\HubAppFileCache
     References:
     MS docs to clear cache
     Some ways to clear cache
2. Local storage is not supported well for web add-in on Windows desktop.
   • localStorage has a size up to 10MB for Outlook on web, but not available on Outlook Desktop
   • indexedDB is not defined on Outlook desktop
   • Office.RoamingSettings is available to all Outlook versions but it is limited to 32KB
3. Errors caused by missing certificate while trying to connect to backend server via HTTPS
   • Error when no cert
     
   • Error when cert has no -ext "EKU=serverAuth" or -dname "CN=localhost"
     
   • Solution:
       Set up the certificate and keystore.jks properly.
       It can use a self-signed cert pointing to localhost.
       The cert must be installed to “Certificates - Local Computer\Trusted Root Certification Authorities”.