Hi @Peter Findinge Frederiksen ,
Welcome to our forum!
May I know whether you have installed Danish proofing tool in File > Options > Language > Office authoring languages and proofing > Add a language?
If so, it is recommended you using the following troubleshooting:
- What detailed version of Outlook are you using?(File > Office Account > About Outlook)
Please make sure your Outlook is updated to be latest, click File > Office Account > Update Options > Update Now - Besides, I’d like to confirm if you have set the preferred language of your Windows to be Danish. If not, try to promote Danish to the top of the list and see if the issue continues.
- If the above doesn't help, try to repair office from control Panel
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