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Old 16 Sep 2020, 06:06 AM   #1
jaybea28309
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Shared Rules between email accounts

I have an old email address which only has a few defined legitimate senders, so it works quite well as a honeypot account, because anything that is sent there from another sender is always spam, and I often see the same spam messages hitting my other accounts.

Is there a way that I can use the messages identified as spam on this account to generate spam filtering rules on my other accounts? It needs something like a set of rules on the master account for the domain which does some high level filtering before the mail hits the rule sets on the individual email accounts.
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Old 16 Sep 2020, 07:14 AM   #2
emoore
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I'm using a legacy account. Do the current plans still support individually trainable bayes databases for each user? If so you could move spam messages from the honeypot to the designated folder in the master account, so that it learns to recognize similar messages as spam. That would be easier and more robust than modifying rules sets in multiple accounts. That folder can be the same folder as your normal spam folder though you might prefer to use a different folder to make it easier to review your normal spam folder for errors that the global spam filtering made.

https://fastmail.blog/2007/08/31/imp...yes-databases/

I use a email client rather than webmail with fastmail and don't have shared accounts so I'm not sure how to automate that. If the new rules system doesn't let you move a message to another accounts mailbox perhaps a Sieve script does.
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Old 16 Sep 2020, 11:41 PM   #3
jaybea28309
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Quote:
Originally Posted by emoore View Post
I use a email client rather than webmail with fastmail and don't have shared accounts so I'm not sure how to automate that. If the new rules system doesn't let you move a message to another accounts mailbox perhaps a Sieve script does.
I use an email client too (TheBat), and I could automatically copy messages categorised as spam in one account into the spam folders of the other accounts using filters, so that could be a useful experiment, although it would only work when the email client on my PC is running.
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Old 20 Sep 2020, 01:00 PM   #4
emoore
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Sieve scripts might let you do what you want. It will run automatically upon the server receiving the new message. Think of it as server side message filtering.

You might be able to use a redirect command in a Sieve script to copy a spam message from the honeypot to a spam folder in another account if you use plus addressing to specify the destination folder as part of the other accounts email address.

I had hoped you might be able to use the fileinto command instead but that doesn't seem to support any way to specify a folder in another account.

See https://www.fastmail.com/help/technical/sieve.html and forwarding messages in https://support.tigertech.net/sieve

See the writeup on plus addressing in https://www.fastmail.com/help/receive/addressing.html
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Old 20 Sep 2020, 05:42 PM   #5
JamesHenderson
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Quote:
Originally Posted by jaybea28309 View Post
Is there a way that I can use the messages identified as spam on this account to generate spam filtering rules on my other accounts? It needs something like a set of rules on the master account for the domain which does some high level filtering before the mail hits the rule sets on the individual email accounts.
Can you forward them directly into your spam folder using the [email protected]<username>.<domain>.<tld> addressing format?

Or autoforward from that account to your normal inbox but have a rule that anything forwarded from that account is marked as read and put into the spam folder?
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Old 22 Sep 2020, 08:39 AM   #6
n5bb
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Are these different accounts completely separate Fastmail accounts where the spam is send directly to the main address or an alias at that account? Or are you discussing several aliases at one account, or an account at a non-Fastmail provider, or emails forwarded (or fetched) from a non-Fastmail account?

Have you gone to the trouble of examining the sending IP address and other details on the similar spam received at the two accounts? Spammers often switch the sending systems to get around spam filtering, and it's quite possible that the spam messages you receive which superficially appear to be similar were sent from different servers and have quite different spam signatures. Spam is quite varied, and unless you are getting slammed with many messages each day which are very similar, it's just not a good use of your time to mess around with custom filtering.

I think that only reasonable solutions are:
  • Using the normal spam filtering systems separately on each account. See:
    https://www.fastmail.com/help/receive/stopspam.html
    If you have learned at least 200 messages as spam and 200 as non-spam, a personal spam filter will be activated automatically for that account. Because I have reported a large number of good message as non-spam, I get very few false positives and have set my spam threshold down to 4.0 for moving to the Spam folder. This setting works well for me, but might not work for others.
  • If you get a large quantity of spam with similar characteristics (such as message content in the subject or body, sending IP address, sending country, etc.), you can create a rule to force such messages to be directed to your spam folder.
    • The easiest way to start on this is to read such a spam message using the Fastmail web or mobile phone client, then do the following:
    • Click More ... Add rule from message ...
    • Edit the conditions at the top. Change, add, or remove conditions if they won't trigger on the spam messages.
    • Check "Sent to spam".
    • You can give this rule a name so you can find it later.
    • Click Save.
    • You can go back and edit this spam rule to add or modify the conditions.
    • In difficult cases, it's possible to add custom sieve code, but with the current system I think this is a waste of your time. The spam system works well if you let it work, and learn >200 spam and non-spam messages (and any commonly received messages) so that your account can learn your situation.
    • Note that received messages are not automatically learned as spam, even if they are auto-filed into your Spam folder by the default system spam filter. You need to force them to be learned as spam after making that decision yourself. I have a folder which is normally empty I created called "SpamReporting" and if I start getting a lot of spam I move those messages into that special folder, then select all messages in that folder and mark them as spam. They will then be automatically moved back to the Spam folder and learned as spam.
  • Although you could look at the spam messages received at one account and create spam filtering rules at the second account based on the characteristics, this is usually just not worth the effort. Let the existing spam filtering system do it's job.
  • I would not forward spam messages from one account to another. You would be risking being classified as a spam sender, and the receiving system may blacklist that Fastmail outgoing SMTP IP or your account. It's always best to mark as spam and then delete incoming messages on the email account which directly received the spam, and never forward a spam message.
Bill

Last edited by n5bb : 22 Sep 2020 at 08:48 AM. Reason: Explained spam learning
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Old 22 Sep 2020, 12:15 PM   #7
xyzzy
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Quote:
Originally Posted by n5bb View Post
I have a folder which is normally empty I created called "SpamReporting" and if I start getting a lot of spam I move those messages into that special folder, then select all messages in that folder and mark them as spam. They will then be automatically moved back to the Spam folder and learned as spam.
Is there some reason you don't just set Spam learning for that folder to spam and possibly also Auto purge after a reasonable amount of time?

Last edited by xyzzy : 22 Sep 2020 at 12:26 PM.
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Old 22 Sep 2020, 02:14 PM   #8
n5bb
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Originally Posted by xyzzy View Post
Is there some reason you don't just set Spam learning for that folder to spam and possibly also Auto purge after a reasonable amount of time?
Good question. I had my folders set up that way a few years ago. But Fastmail (in their help and in mypersonal email communication with staff) strongly recommends not setting the Spam folder for learning. This is due to the spam feedback learning loop which is created. For example:
  • Let's say the Spam folder is set to learn messages as spam, with auto-purge set to 31 days. You might think that this would give you a full four weeks to get around to checking the Spam folder for false positives (ham treated as spam).
  • Now let's say that your bank (or some other source) sends you two emails a day. In some cases the From address is not fixed, so you might not have it in you address book to whitelist. If one of those messages eventually exceeds the spam threshold (let's say one every six months), that message will be moved to the Spam folder and the folder settings will learn it as spam.
  • Now emails from that same sender (or with similar spam indicators such as certain words or the sender reputation) will receive a higher spam score. So if the probability of a message from that sender was 0.1% one week, it might be 1% a couple of weeks later, and before long it's over 10%.
  • You won't lose any ham (desirable) messages if you look at the Spam folder at least every 30 days. But more and more of the ham messages from that source will be missing from your Inbox, and since it's a somewhat random process it would be very aggravating!
  • So how do you fix this problem? You could manually learn every false positive as not-spam, but that takes a lot of work! You could try to add a special rule to whitelist those emails, and that's also a pain. And now you need to look at the Spam folder several times a day to be sure you haven't missed an important message. This defeats the reason we use spam filters!
  • This is much less of an issue for false negatives, which are spammy email which doesn't get caught by the spam filter and so get learned as not-spam. The spam messages which are learned in a feedback loop as not-spam will probably eventually change or go away when Fastmail starts blocking them at the SMTP stage.
  • So it's best to not set the Spam folder to learn spam.
Bill
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Old 22 Sep 2020, 03:25 PM   #9
xyzzy
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Originally Posted by n5bb View Post
So it's best to not set the Spam folder to learn spam.
My questions wasn't referring to the actual Spam folder. I was referring to that "SpamReporting" folder you mentioned.

With respect to the actual Spam folder, I agree you should never set that folder's Spam learning to spam since that may falsely mark a message as spam if you don't intercept it before Spam learning's daily check. Not setting Spam learning (as recommended) gives you the opportunity to mark messages as not spam since stuff is learned as spam in the Spam folder only when you explicitly delete those items from the Spam folder. I believe this is why it's done that way.

I guess this reasoning could be applied to other folders too (e.g., that "SpamReporting" folder) but I assumed you only put stuff in there that you knew was actually known to be spam.
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Old 22 Sep 2020, 06:03 PM   #10
JamesHenderson
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Quote:
Originally Posted by xyzzy View Post
With respect to the actual Spam folder, I agree you should never set that folder's Spam learning to spam since that may falsely mark a message as spam if you don't intercept it before Spam learning's daily check. Not setting Spam learning (as recommended) gives you the opportunity to mark messages as not spam since stuff is learned as spam in the Spam folder only when you explicitly delete those items from the Spam folder. I believe this is why it's done that way.
So, if I delete something from the spam folder as it is neither spam nor of particular interest, it gets learned as spam? ...or does it only learn the spam when fastmail auto-purges after 90 days?
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Old 22 Sep 2020, 08:36 PM   #11
xyzzy
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Originally Posted by JamesHenderson View Post
So, if I delete something from the spam folder as it is neither spam nor of particular interest, it gets learned as spam? ...or does it only learn the spam when fastmail auto-purges after 90 days?
I believe either way (explicit "manual" delete or auto-purge) it will try to train the spam filters when the message is deleted from the Spam folder.

Heh! I wonder what would happen if you did set the Spam folder to auto-purge but as "not spam"! I would assume no one would actually do that but the UI apparently doesn't stop you from doing it.

Update:
I think a more generalized way to describe what's going on would be to say deleting or moving stuff into or out of the Spam folder updates spam/non-spam learning at the time of the delete or move.

Last edited by xyzzy : 22 Sep 2020 at 09:43 PM.
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