With the amazing load of spam coming at email systems dayly, admins may be faced with the choice of delivering messages that are almost certainly spam to a quarantine mailbox, or deleting them.
From a technical perspective, email is a best effort service, and while that best effort is pretty darn good, we all know that there are several things that can prevent an email from reaching an inbox. From an end user perspective, email is considered as reliable, and virtually as fast, as a phone call, and anything that prevents a critical business communication from reaching its intended recipient may be unacceptable.
When filtering emails coming into your organisation, one thing you have to decide upon early on in your design is what to do with all of the email determined to be spam. Several factors may need to be taken into consideration before you decide what to do with spam: do you delete all spam messages, or do you move them to a quarantine mailbox?
Moving email to a quarantine folder might seem like the best option (and for some businesses, it will be) but there can be significant overheads. Someone will need to be tasked with regularly reviewing the quarantine folder, releasing messages that are false positives, and emptying the folder of actual spam. Otherwise, the help desk will need to process tickets every day to search for a message that never arrived.
You could also consider an antispam solution that delivers spam to a user’s junk mail folder or other self- service area, and that automatically deletes all messages older than a certain number of days to let the users help themselves without using up all your disk space.
Speaking of disk space, quarantine folders can get really big in a hurry. Conservative estimates put the percentage of email that is spam at over 50%, with my own experience being closer to 80%. All that spam that you are not deleting has to be stored somewhere, which if not a reason to delete immediately, is certainly a strong argument for a shorter retention period.