Here’s how you fix that, step by step, right from your mobile device.
Tap your profile icon (top-left corner) or the three horizontal lines to open the sidebar. Scroll down and tap Settings (gear icon).
Sometimes, after unblocking, old emails stay in Spam. Go back to your inbox, open the Spam folder, find any messages from that sender, and mark them “Not Spam” to retrain Yahoo’s filter.
In Settings, look under “Managing your account” or “Advanced” — on most recent versions, tap Blocked addresses . (On some older layouts, it might be under “Security and Privacy.”)
Ask the person to send a quick test email, or send yourself a message from that address if possible. It should land right in your main inbox.
You’ll see a list of blocked emails or domains. Find the one you need to unblock — maybe that colleague whose reply kept bouncing, or a store you actually do want to hear from.