How to Identify Authenticated Senders and Avoid Phishing in Gmail

An ace, clubs; a ten of clubs; a king and then a four, both clubs; another ace, spades.
Now, a pair of aces is nothing to be ashamed of. We're just one card shy of a flush, though, and this is poker, after all. Let's pretend — only in our mind and face, perhaps — we had, say, a six of clubs instead of the ace of spades: not a straight flush, in full, but a respectable hand.
We're "four-flushers" now, bluffing and swindling cheaply; it does not take a four-flusher to recognize another in email, though. It takes authenticated senders and Gmail, for example:
›› In Gmail, you can know for sure certain messages came from certain senders with the gold key authenticated sender icon.