Instead of a simple ding sound, it's possible to have Mail tell you a little more about incoming messages using speech synthesis. Create the following AppleScript in Script Editor:
using terms from application "Mail"
on perform mail action with messages newMessages
repeat with newMessage in newMessages
tell application "Mail"
set senderName to (extract name from sender of newMessage)
say "You've just received an email from " & senderName
end tell
end repeat
end perform mail action with messages
end using terms from
Save it to something like ~/Library/Scripts/Mail Reader.scpt. In Mail, create a new rule to run the script on every incoming message.
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