Is there an Inbox icon showing if I've replied to an message?

[gbtbag]

It drives me nuts that I have to open an email or go into my "sent" folder to
see if I've replied.

Is there an icon which can be added to the emails in the Inbox to which I've
replied?

Forgive me for mentioning the A word but in my Mac mail program, I can see
immediately whether or not I've replied without having to open the message
because there is a little arrow indicating I've responded.

Unfortunately, I have to use Outlook at work. It would make life so much
easier if I could just see a check mark in one of the columns showing I've
replied to that email without having to trawl through every message.

 

[Roady [MVP]]

Outlook has that too by default but this may not work for or not be visible
to you for various of reasons. It really depends on the configuration
details why it might not work for you now.
See http://www.msoutlook.info/question/291