Accounts non-browser activity

[fuzguz]

Hi.
I'm fairly new using zimbra so please forgive me if this is mentioned somewhere or if its super easy. I took over administrating mail server and i need to clear old account not being used. Problem is account say never logged in but I know for a fact that some of those accounts are being used on outlook or thunderbird.
Is there a way to find accounts that have not used pop or imap in a while?