I don't think so. I want a log of what Mail App on my iMac is calling junk not what is coming via my mail server.
If I can access the Mail App log I can then create a blacklist on the server.
All I want to do is create a text file of addresses from what OSX Mail is marking as junk. This has nothing to do with my ISP.
Mail doesn't mark addresses as Junk. It marks messages as Junk. Mail's filter is based on an analysis of the text of the message. The address has nothing to do with it.
Here is a semi-technical article.
Given that the Junk filter is so accurate on what it does fillter, it's only sensible that those email addresses are also Junk/Spam, and that is what I can plug into my server.
Having said that I've found an app which can extract addresses from mbox files so that should do the trick for me.
Filtering junk by sender address is generally a fruitless operation. Spammers use phoney addresses — they would get caught if they didn't — and they change the addresses frequently. That's why Mail's Junk filter doesn't use addresses.
Just looking at my Junk mailbox from about the last few weeks, the eight most recent messages are the same message from eight different senders. Two other recent junk messages appear to be, but are not, from family members. Often spam appears to come from someone you know.