Email gone in Exchange for Windows SBS 2003

Our company is using windows SBS 2003 with exchange and when the email account has exceed it’s limit, we can’t send or receive anymore email which is normal

This email account is connected to a Pop3 account using “Pop3 connector manager”. We have enlarge the limit of this account but we found that during that period of few days when it has exceed it’s limit, the emails have gone missing, we know for sure it has been downloaded to exchange because we checked the pop account and saw a list of email still there before being downloaded by exchange.

The question is, are these emails gone for good or are they in one of the temporary folders in windows sbs 2003 during the time when the email has exceeded its limits. Thanks