A running count is kept of Unseen messages for each folder. Very occasionally the count against one or more folders may become incorrect, and this facility will quickly correct this - it clears the running count and gets an up-to-date and correct count from the database.
Please see the page devoted to this subject for further information.
The more robust database used from version 11 means that few utilities are needed.
Should you believe that you have suffered from data corruption (which we believe will be very rare), please contact MailCOPA Support giving as many details of your problem as possible. It may be necessary for you to send your data to us for examination and repair - there is an easy mechanism for this.