VPOP3 2.x usually uses SQLite 2.8.3 as its database engine. This stores databases in discrete *.db files in the VPOP3\_database directory on the server PC. We do not recommend that you access these databases directly unless you know what you are doing, and we strongly discourage the alteration of data in the databases directly unless technical support request you to.
logdb.db - this contains historical logging information for reports. It can be configured/disabled on the Logging → Admin logs page in the 'Historical Logging' section.
spamfilter.db - this contains statistical information for the Bayesian filter section of the VPOP3 spam filter
msgids.db - this contains summary information on the last few days' worth of emails, for duplicate detection
archive*.db - this contains index information for the message archive facility in VPOP3. In older versions of VPOP3, there is a single archive.db file. In later versions there are archive<MM><YYYY>.db files for each month.
user_*.db - these contain mailbox index information for the individual users
quarantine.db - this contains information about messages which ahave been quarantined by the VPOP3 content/spam filter.
Whilst VPOP3 is stopped, certain database files can be deleted if they are corrupt without causing major problems, others can be deleted, but will cause problems if they are. If any database is deleted, VPOP3 will automatically create a new (empty) one when it restarts. Below is information about deleting the databases.
Note that we do not recommend deleting any of the databases in normal operation (otherwise VPOP3 would delete them for you, or they simply wouldn't be made).
logdb.db - this can be deleted. You will lose historical logging information, but nothing else.
msgids.db - this can be deleted. You may receive a few duplicate messages (depending on how your Internet connection is configured), but that will resolve after a few days.
spamfilter.db - this can be deleted, but the spamfilter will be less effective for a while.
archive*.db - these should not be deleted. If you delete these files you will lose the facility to search or backup the messages which have already been archived.
user_*.db - these should not be deleted. If they are deleted, you will not lose any messages, but you will lose any IMAP4/Webmail message flags (eg read, answered etc)
quarantine.db - this should not be deleted. If you delete this file, VPOP3 will lose the facility to access or tidy up any messages which are in the VPOP3 quarantine.