Hey all, I have a general question/suggestion regarding Sieve.
It seems to me that it would be useful to be able to install filter plugins that could transform mail messages as they were processed. This would be a simple command, like: filter :spamassassin This command would take the email, shove it through the "spamassassin" filter on standard in and read the email back from standard out. On any kind of execution failure it would treat the filter as a noop and use the email as it was prior to injection. It would also be useful for the filter to be able to communicate information back to the sieve script for branching or decision making purposes. To keep the language ultra simple like it currently is, my first proposal would be that a filter would insert or change an email header to add the info that the script would then check. So on the above spamassassin filter the sieve script post filter command would check the "X-Spam-Status" header to see if it contained "Yes,". Now given that Sieve is also supposed to be used from the GUI of email clients to construct filtering rules, and that filters are variable from one server to the next, this would require the client to contact the sieve server and request the list of installed filters. I haven't worked out all the details of how a client and server exchange this information, especially how does a server tell a client that list they requested is now different and it needs to get a new list or what does a client do when it has a script that uses a filter that isn't in the list of server choices. To get around that I'm thinking that for now, the end user just has to magically know (by being told by their administrator) what the current list of filters are and the client GUI then just has to provide a type in field where the end user writes the plugin name. A drop down list might be more user friendly but I think it complicates what is currently a very simple language. What do others think about this? Would this simple "pass through" filtering be useful? I'm primarily thinking of Spam catchers, Virus Scanners, and any other use where shoving the email through an external application would be useful. Ideally I'd love to have a "Bayesian Classifier" filter that periodically goes through my folders and creates profiles based on emails in each folder. Then I shove the incoming mail through the filter and and have it tell the sieve script where to file the email. However I can't get around needing a return variable from the script, or at least a regular expression matcher that could extract the chosen folder from a header the classifier inserted into the email. I could do a huge elsif header :contains "Bates-Class" "<foldername>" block, but then I need to update the sieve script every time I create/delete a folder like I do now every time I join a mailing list. Any feedback would be appreciated pro/con/flame/other. Thanks, -- Michael --
