It's been said that eBay slaps you with cookies when you open up certain emails from them. Usually the random emails, about promotions, questionnaires, those sorts. These cookies, once loaded into your browser can send information back to eBay once you sign into your eBay account.
There have been a few people suggesting this, and others saying eBay doesn't do this. In some ways, I know eBay implants beacons in their messages which does send information back to eBay servers, though I don't think they use that information other then statistics.
Though I will say, it's never a good idea to open any email from a suspended eBay account. The only way I would do it, is from another machine then my primary one. I've always done this, maybe for this reason, or paranoia, but it seemed to work, and I've had less linked accounts because of it.
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