I never had a mail checker that worked with any email....ever. Even the one in Winstep tells me an inaccurate number of emails.
No disrespect, but perhaps you don't fully understand how email checkers work then. From the Winstep Xtreme FAQ:
The Email Checker is not a full blown email client. The Email Checker simply asks the server how many messages are pending retrieval, and, if there are any, that's what it reports. It also keeps a counter of the number of messages in the server so it will only notify you again when more mail arrives. The notification, however, will tell you the total number of messages still in the server, not the number of messages that arrived between the new and previous notifications.
This counter is reset when the number of messages in the server is less than the value in the counter (which means mail has been retrieved in the mean time) or when you tell the Checker to launch the email client.
The Email Checker has no way of knowing which messages have already been read but left on the server.
Also, the Winstep Email Checker was one of the very few (and possibly the very first) that was able to work with Gmail accounts, but that ended when SSL v2 was found to be insecure in 2009 and the email providers stopped allowing connections encrypted with it. Unlike most normal POP3 email servers, Gmail, Hotmail and Yahoo mail all require a SSL encrypted connection, which the Winstep Email Checker provided - but only version 2. SSL v3 support is a whole different beast to implement.
The Winstep Email Checker is probably still the only Email Checker that offers support for IMAP accounts.