The first question — whether you have replied to an email — is answered by the small leftward-swung arrow in the message list in Mac OS X Mail.
But what about the second question — what exactly you wrote in your reply? Do you have to dig and search the Sent folder? No, the small arrow has the answer to this question, too.
Find Your Reply to an Email Fast in Mac OS X Mail
To find your reply to an email fast in Mac OS X Mail:
- Click on the leftward-pointing circled arrow for the message in the status column of the message list (where flags and the unread marker appear).
- In earlier versions of Mail, the arrow may be in the Flags column.
Mac OS X Mail automatically opens your reply in a new message window. If you have answered an email more than once, only the last answer will open.
(Updated September 2012)