In a browser tab (or window) opened by clicking on a link in an OTRS email, Javascript-related MediaWiki functions do not work (e.g. if you try to edit Wikipedia/Commons, clicking on the Save button does not do anything; UploadWizard doesn't even load). The browser console will say something like Blocked script execution in 'SOME URL' because the document's frame is sandboxed and the 'allow-scripts' permission is not set.
This is supposed to be an OTRS security feature (email content is sandboxed with a allow-same-origin allow-popup setting). A workaround is to open new tabs via right click + "Open in new tab" instead of simply clicking on the link (might be browser-dependent; confirmed in Chrome 45).
Only affects HTML emails, not plain text emails (as a rule of thumb, emails which ave blue links and normal fonts are affected, those with orange links and monotype fonts are not).