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Not seeing this with my Gmail account. It's a paid account, though. Maybe that's the price for good, free email.

It does seem to behave differently for paid. For example, it doesn't give you automated suggestions on what to respond, which hints that it might not be reading your mail.

Not sure about gmail, but its been this way for awhile with gchat and i'd presume gmail too.

I think it's less for tracking than for trying to combat viruses and phishing attempts. Having the spool data and writing the JavaScript mail client app makes link-based tracking redundant.

Gmail Tracking All Links