I often forward on emails such as Google Alerts or newsletters. But a problem with this is many senders try to make things easier for you, so they have one-click unsubscribe links, or auto-sign-in links for managing your account. This is great for the primary recipient, but can result in serious trouble should a forwardee decide to click one of those links. (And I'm sure it's not with malicious intent. It's easy for someone to get confused by such links in a forwarded email and think they apply to you and not the original recipient.)
So before hitting send, I make a point of always scrolling down to the footer of the message and deleting any manage and unsubscribe links there to avoid any inadvertent settings changes.
I learned this the hard way with Google Alerts, where a forwardee ended up unsubscribing me from my own alert. 😛
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