Hi @Velasquez, Patricia ,
Thanks for your reply!
Based on my research, i found that it may be related to a fixed issue as shown in the below image, what's the version of your Outlook desktop client?(File > Office Account > About Outlook). It's suggested that you could update your Outlook to the latest version to check if there're any difference. More information: Known issues with sensitivity labels in Office.
If it doesn't work, according to a similar thread as yours, which mentioned that this pop-up may indicate your organization has assigned an information protect policy to this mailbox to enforce labeling on emails. It's suggested that you could try to label the email: Apply sensitivity labels to your files and email.
Hope to help you!
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