Message previews omit plain-text image labels when the message contains images and show (No text) when no text remains. Stored messages and attachments are unchanged. Mail checks for new messages every 5 seconds during active use, slowing to every 15 seconds after 5 idle minutes, every minute after 15 minutes, and every 5 minutes after 30 minutes. Hidden tabs stop checking; returning or interacting restores frequent checks. A refresh postponed during message selection is retried afterward.
Mail previews and faster new-mail checks
Image-only messages show (No text), and active Mail checks for new messages every 5 seconds.