Where is the data held, and what do all of the files do?
Under Windows 98 & ME:
C:\Program Files\MailCOPA\data
Under Windows 2000/XP/2003
C:\Documents and Settings\All Users\Application Data\InterVations\mailcopa
Under Windows Vista, 7, 2008, 8 & 2012
C:\ProgramData\InterVations\MailCOPA
You can find out exactly where the MailCOPA email client is looking for data by going to the MailCOPA configuration menu, selecting Set Preferences and going to the Global settings page. There you will find a field marked Data Path.
These files are part of a proprietary database, which you should absolutely leave alone unless instructed by MailCOPA Support. There is no way of accessing them except via MailCOPA itself - the messages themselves are compressed (to a proprietary algorithm).
It is possible that you will be asked to send copies of specific files to the MailCOPA email program Support Department in the event of problems. Any data sent in this way will be dealt with confidentially, and will be destroyed once the problem has been solved.