Ticket number duplication

Hi,

We have experience ticket number duplication occurring randomly. We pull mail from around 80 mailboxes on a cron time of every 15 minutes.

Any recommendations would be appreciated

Make sure the cron job has enough time to complete before the next one is executed. If you have overlapping crons then you will have overlapping data/numbers, etc.
Make sure you don't have auto-cron enabled if you have a working cron job. Again, this will cause overlapping cron which causes overlapping data, etc.

Cheers.

I do not have auto-cron enabled but will extend the cron job time and monitor.