An important message might be hiding in spam
If a message you're expecting hasn't shown up, checking the spam folder first is worth it -- spam filters flag legitimate mail by mistake more often than people expect.
Adding a sender to your contacts helps the filter learn
If a legitimate sender keeps getting flagged even after you mark their mail 'Not spam' once, adding that address to your contacts gives the filter a stronger signal to recognize it as trusted going forward.
Frequently Asked Questions
A legitimate sender's mail keeps landing in spam. What should I do?
If marking it 'Not spam' repeatedly doesn't fix it, adding that sender to your contacts usually helps the filter learn to recognize their mail as trusted.
What happens when I block someone?
Future mail from that address is automatically routed to spam, and the sender isn't directly notified that they've been blocked.