Synology Diskstation: How to avoid junk mail drop into junk folder

It seems rather odd in the title. However, the problem arises when the email client is using POP, the server side's junk folder cannot be accessed without using the web client (Roundcube). Normally, there are two solutions for the case, i) disable the spam control function in the server; ii) add into the white list. Both of them have their disadvantages and I have found another alternative: let the problem emails still have the "SPAM" marks but keep in the inbox so that users can read them via their email clients.

There are few documents around the Internet to tell how to do it. After studying for sometime, I finally found our the methods (works in DMS 4.3). The component related is a little Dovecote plugin called "Sieve". Which it has a little script to do the work:

/volume1/@appstore/MailServer/scripts/sieve_before/move_spam.sieve

The script is somthing look like:

require "fileinto";

if header :contains "X-Spam-Flag" "YES" {
         fileinto "Junk";
}

The script means that whenever the SPAM engine marked the email as junk, the plugin will move it from the inbox to the junk folder. Just use the "#" comment marks to comment the lines will do the job. Is it simple? However, I really spent more than an hour to find the solution!

Also there is a file called "move_spam.svbin" in the folder, It is the compiled file and just leave it there. It will be recompiled automatically whenever there are changes in the above script file.

Reference:

http://wiki2.dovecot.org/Pigeonhole/Sieve/Examples