Several users haven encountered issues when using the Microsoft Outlook app.
One possible cause were the various Add-Ins that are selected in Outlook.
You can unselect unused add-ins, select File -> Options -> Add-Ins -> Go
Check that only the following are selected(if you don't use the SmartTMS link, you can untick Pivotal Integration as well) and click OK button
If the issue persists, please send an email to IT Issues
https://competenz.freshservice.com/support/solutions/articles/5000094836