Identifying mail marked as junk; marking and unmarking mail as junk I use several different macs to read my mail from an imap server. Each has developed its own junk mail filtering rules. I'd like to merge the rules, and keep them merged. 


Is there a way to merge the rules from different systems?
Has anyone done anything similar? If so, how? 


A manual approach that would achieve the desired result would be to enter, from each system, the junk mail folder, identify those messages that are not - on that system - marked as junk, and mark them as junk. This requires some way to identify those e-mails that are not marked as junk. I've been unable to find a mail rule query that allows me to do that.  


Is there a mail rule query to identify mails not marked as junk? 


Another manual approach, which I can use moving forward, is to create a custom junk mail action that, in addition to marking the mail as junk, adds a MailTags keyword with the system name. I can then, periodically, find all mail in my junk mail folder that is not appropriately tagged and manually mark it as mail. (While not convenient it is not so inconvenient that I wouldn't periodically do it.) This requires a mail action that marks mail as junk. I've been unable to find a mail rule action that marks mail as junk.


Is there a mail rule action that marks identified mail as junk?


Finally, 


Has anyone any practical (i.e., not so cumbersome as to be unusable in practice) alternate suggestions?


Thanks very much for any and all help and suggestions. 

Best

Sam
Many mail servers have their own spam filters and will add a special header to the message to indicate spam (some are yes/no, others will use a number system where higher numbers indicate the more likelihood the message is spam)

Select a message and Select View -> Message -> Raw Source from Mails menu to see all the headers and info. You may see something like this (highlighted):

 

Based on what you find, you may set up a rule based these headers. (in Mail -> Preferences -> Rules, you may need to add the header in mail (see img))



Repeat this for each Mail client.

As for Mail.app's custom heuristics... That's a bit trickier, but if you are consistent they should end up pretty close on each machine. (I tend to trust my server's filtering more anyway)