Duplicate tickets from spool file

[lradnai]

Hi OTRS gurus!

We have some files in /opt/otrs/var/spool folder for several reasons (unprocessable email, database was down for a while, etc).
The daily scheduled "SpoolMailsReprocess.pm" tries to reprocess these files but it seems so, it does not delete the successfully processed files.
The problem is that this leads to duplication of tickets (from the same spool file) every day.

Questions:
Which module (or sysconfig setting) would be responsible for delete the successfully reprocessed files from the spool directory?
Is there any way to know which ticket was created from which spool file?

Our system is OTRS 5.0.17 + Oracle.

Thanks

lradnai