Download Filters can be used to filter mail from a POP server, before they are completely downloaded; you can use them to prevent KMail from downloading huge messages and save time this way.
In the configuration dialog of the POP account you can enable download filtering by checking the Filter messages if they are greater than box; once you have done that, you can specify a size which is used as a threshold: messages exceeding this size will be checked against the filter rules you defined -- if no filter rule matches, they will be shown in a confirmation dialog and you can decide what to do with them. The default size for filtering is 50,000 Bytes; this is a good value as the overhead is kept to a minimum -- every message that is looked at by the filter causes additional traffic because the header of the message is downloaded twice. The default action is Download mail to prevent the loss of messages.
Be careful with the Delete mail from server option since once a mail is deleted on the server there is no way to get it back.
With a really good set of filter rules, it is possible that all messages that exceed the threshold size are automatically tagged (i.e. downloaded, kept on the server or deleted) and you would never be bugged by the confirmation dialog. Be careful though, since once a message is matched by a filter rule, you have no guarantee that you can change the action before it is executed: the confirmation dialog will be displayed only if there is a message left that was not matched by a filter rule.
Adding filter rules works similar as for message filters. On the left hand side you can manage the existing filters. Use the New button to add a filter. On the right hand side you can configure under which conditions the current filter should match. Using Filter Action you specify what will happen to a message that is matched by this rule. The available options are:
Will download the messages matched by the filter, just as any other message that does not exceed the threshold size.
Will tag the messages for later download. This means the messages matched will stay on the POP server until you choose to download them by changing the action manually.
Will delete the message from the server and does not download it. Once you deleted a message from the server, there is no way you can undo this. Be careful, as rules could match messages you actually want, too.
The option Always show matched 'Download Later' messages in confirmation dialog will cause the confirmation dialog to show up during mailbox check if at least one message was tagged for Download Later - even if all messages exceeding the threshold size were matched by a rule. This option is useful in the case you have messages matched by a rule and tagged for Download Later, but you do not get any message exceeding the size limit for a very long time. Without this option, the confirmation dialog would never show up and you would never have a chance to get the queued message by changing the action manually.
This dialog shows up whenever you have POP filtering switched on and messages were found on the server that exceed the threshold size you defined for the POP account. Now you have the chance to decide what you want to do with that message. The options are Download (green), Download later (yellow with egg watch) and Delete from server (red “X”). Be cautious with the delete option, since once you deleted a mail from the server, there is no way to undelete it again.
In the Filtered Messages section you can check the box if you receive messages that were automatically tagged for a certain action (download, download later, delete) by a filter rule. The checkbox is only enabled if you receive some messages that were matched by a filter rule; once you check it, a list similar to the one for the not-automatically-tagged messages will be displayed and you can change the action for every single message.
Please note that if there is a message exceeding the size limit, but all messages are matched by a filter rule the dialog will not be displayed. One exception occurs if you have checked Always show matched 'Download Later' messages in the Global Options section of the POP filter configuration dialog; then, the dialog will also be displayed if you only have matched messages, but at least one message was tagged for Download later.
Would you like to make a comment or contribute an update to this page?
Send feedback to the KDE Docs Team