Gmail for android silently overwrites links in your emails, so it can track what you open
I clicked on a link inside an email from a privacy service, and was surprised to see they used google tracking for their stuff, so I opened it in thunderbird and behold, it had no tracking.
But the worst part is... if I went back again and long pressed the link on gmail, it showed the link preview, WITHOUT the tracking. There's some kind of rule, so try it first on a new, unopened email, without long clicking. You'll need something to intercept it because the browser will just redirect to the main link.
Imagine the mailman looking at you, noting down which letters you open, it's crazy.
I noticed this thanks to link eye, an app that intercept all browser links and shows a list of supported apps, so you can redirect to the preferred one. It also displays the link, it's abandoned but still working.
I'm 99% sure I have all the privacy stuff set correctly. I suppose it may also happen on desktop/ios, but I have no way to check it
Also fedia is not showing me a field to set the post title, so I'm sorry if everything ends up in the title or if the title is empty
long press
opened link
But does it do this even if you access Outlook from the web at: outlook.office365.com
That's what I do for my work; I don't have the app installed and just check manually.
When I access through Thunderbird via IMAP the emails have been rewritten. It's not local to the Outlook client software.
I think my webmail is
outlook.office.com, dunno if that's the same asoutlook.office365.com. It may be a org/account setting managed by my org. Maybe you also don't receive emails with unlabeled links, where it's very obvious that they're replaced. On linked text, only if you notice the URL you're opening.