By default Blue Host uses the Dovecot IMAP servers, exim as the MTA, and stores email messes in Maildir format within a /home/account-name/mail/example.com/mail/email-address style structure.
Individual emails tat have been read can be found in:
/home/account/mail/example.com/address/cur
Individual emails tat have been read can be found in:
/home/account/mail/example.com/address/cur