Interesting. This seems to be the case in some institutions where external URLs are redirected through some form of filters (e.g. TrendMicro) to detect phishing attempts.
There were some discussions online about accidental unsubscribes. Some suggested implementing a manual click-to-unsubscribe at a webpage instead of one-click unsubscribe.
Microsoft mentions activation of links in a sandbox environment for threat-detection purposes.
Attachments or links in the email are opened inside a sandbox environment where the content is analyzed by our machine learning models that check for malicious signals and apply deep link inspection, allowing for zero-day malicious attachments and links to be detected