Hi @Ruben Siegrist ,
In order to better identify the problem, please provide the following information:
- What's the version of your Outlook 2016 ? (File > Office Account > About Outlook). Please make sure you have upgraded your Outlook to the latest version.
- Does the issue occur only in specific account? If you use other types of account testing, such as Exchange, will the problem arise?
- Does this issue occur in some specific emails? And are these emails opened of your account or of some shared mailbox?
Through my research, considering the impact of some add ins, It is suggested that you could try to start outlook in safe mode(win+R>type: outlook /safe) to check whether it works normally.
If your issue has any update, please feel free to post back.
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