Hi,
I can reproduce your this issue in Outlook 2016. But the screentip can be seen properly in OWA or other mail clients.
After further research, I found that this is by design that the Screentips won't show up in Outlook client to avoid the link obfuscation attacks. For example, if the ScreenTips feature is available for Outlook messages, someone may add a screentip which
shows the safe text for a harmful site.
My understanding is that the Outlook product team did this for security concern of Outlook emails. If you have more concerns about this feature, we can submit a feedback in Outlook Suggestion Box:
https://outlook.uservoice.com
It is a place for customers provide feedback about Outlook for Windows. What’s more, if a feedback is high voted there by other customers, it will be promising that Microsoft Product Team will take it into consideration when designing the next version in the
future.
Hope you can find the above information helpful.
Best regards,
Yuki Sun
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