Download rules are a facility in VPOP3 where it can look at message summary information before downloading a message from an ISP POP3 mailbox (they do not work on incoming SMTP messages - use SMTP Rules for that)
Download rules can only see message headers, message size, and other information such as current date/time, etc. They can not see message content or attachments etc. This is because download rules apply before the message is downloaded. If you need to check the message content, then you may need to use the spam filter rules.
There can be multiple download rules created. VPOP3 checks the download rules in order from top to bottom. When it finds a download rule which matches, then it will not process any further rules.
Each rule has zero or more conditions. If a rule has zero conditions, then it will always match. If it has more than one condition, then you can set whether it checks that all the conditions match, or that any one (or more) of the conditions match. You cannot mix 'all' and 'any' checks within a single rule.
Each rule can cause one action.
There are several actions that a download rule can cause:
Note that with any of the 'Delete' or 'Silently Delete' actions, we recommend testing the rules with a different action, such as 'redirect', in case you make a mistake with the conditions.
The conditions that VPOP3 can check for a rule are:
VPOP3 logs download rule activations in a file 'dlrules.log' in the VPOP3 logging directory.