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RABiD BUNNY FEVER
K.T.K

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Useful Exim Scripts
For fighting spam

In the course of my Linux administrative duties (on a cPanel server), I have created multiple scripts to help us out with Exim, our mail transfer agent. These are mostly used to help us fight spam, and determine who is spamming when it occurs.



This monitors the number of emails in the queue, and sends ours admins an email when a limit (1000) is reached. It would need to be run on a schedule (via cron).
#!/bin/bash
export AdminEmailList="ADMIN EMAIL LIST SEPARATED BY COMMAS HERE"
export Num=`/usr/sbin/exim -bpc`
if [ $Num -gt 1000 ]; then
        echo "Too many emails! $Num" | /usr/sbin/sendmail -v "$AdminEmailList"
        #Here might be a good place to delete emails with “undeliverable” strings within them
        #Example (See the 3rd script): exim-delete-messages-with 'A message that you sent could not be delivered'
fi

This deletes any emails in the queue from or to a specified email address (first parameter). If the address is the recipient, the from must be "<>" (root)
#!/bin/bash
exiqgrep -ir $1 -f '<>' | xargs exim -Mrm
exiqgrep -if $1 | xargs exim -Mrm

This deletes any emails in the queue which contain a given string (first parameter)
#!/bin/bash
if [ "$1" == "" ]
then
  echo 'Cannot delete with empty string'
else
  grep -lir "$1" /var/spool/exim/input/ | sed -e 's/^.*\/\([a-zA-Z0-9-]*\)-[DH]$/\1/g' | xargs /usr/sbin/exim -Mrm
fi

Get a count of emails in the queue per sender (sender email address is supplied by sender and can be faked)
#!/bin/bash
exim -bp | grep -oP '<.*?>' | sort | uniq -c | sort -n

Get a count of emails in the queue per account (running this script can take a little while)
#!/bin/bash
exim -bp | grep -Po '(?<= )[-\w]+(?= <)' | xargs -n1 exim -Mvh | grep -ioP '(?<=auth_sender ).*$' | sort | uniq -c

Bonus: Force all non-specified accounts on Exim to use a certain IP address for sending. It would need to be run on a schedule (via cron).
#!/bin/bash
export IPAddress="YOUR ADDRESS HERE"
/usr/bin/perl -i -pe 's/\*:.*/*: '$IPAddress'/g' /etc/mailips
SpamSoap
Info on a spam filtering solution

I was long ago pointed to SpamSoap by a friend who helped lead the IT department of a rather large and prestigious law firm. It seems to be an excellent spam filtering solution, but can get to be rather expensive as it is a pay per month per mailbox program, kind of (you pay in groups, like 1-5, 6-10, ..., 201-250, etc). I wouldn’t mind too much trying out the filtering with Google’s domain email program, but Google has marked multiple legitimate emails as spam in my Gmail account in the past, and I don’t trust their cloud computing approach too much with my data.

I originally set up a SpamSoap account 2 to 3 years ago for a single client, and have more recently been setting it up for myself, family, and some other clients. The client that has been using it for that time has been very happy with it, and the only reason I didn’t start using it for myself and others at that time was because it marked a legitimate email as spam for me, and diagnosing why didn’t get very far with their tech support. I have however done a lot more research into their system recently, asking their staff lots and lots of questions to understand the system more, and believe I know why it was caught as spam. Unfortunately, their documentation is horrible and their site doesn’t really go into details at all, so information on how it all works and how to set some things up is not easy to come by. The problem, in my case, is that where the email arrives from to the SpamSoap servers is considered. Servers that SpamSoap receives a lot of spam from are marked as more likely to be sending spam, so unfortunately, forwarding emails from another address to an address on a domain filtered by SpamSoap is a bad idea, as then the whole server that manages the domain that is forwarding is marked as sending a spam message. However, this is only one of many spam determining metrics used, and, of course, it takes many spam messages to make a difference for a server, but if you are forwarding from an address that receives a lot, bad things happen :-). Anyways, here’s some of the information I gathered on how their system works, and other important tidbits, if anyone is interested in using them.


The way SpamSoap works is you pay for “user accounts”. Each user account has 1 white/black list associated with it (which isn’t technically needed, but helps things along), 1 quarantine area, and receives (if they choose too) daily quarantine reports to their master address. Each user account can have email aliases tied to it, but due to the quarantine area it’s important to separate users. Pricing is based upon number of user accounts in tiers, like 1-5=$15/month, 6-10=$25/month, 11-20=$42/month, and so on.

The actual filtering is done by setting MX records for the domains to be filtered to SpamSoap, and SpamSoap actually just sets up a proxy connection between the sending server and your server for delivery. If a message is detected as spam during this process, the delivery attempt is canceled.

There are 2 types of incoming spam that can be filtered different ways by the system; high scoring (100% likelihood) spam, and medium scoring (>90% or something like that, an exact number is not obtainable) spam. With either of these you can choose to either: Tag the message with “[SPAM]” in the header, quarantine the message, deny delivery, or let it through. There are also filtering rules and actions you can set up on based other criteria, like: viruses, content (profanity, racial insensitivity, sexual overtones, etc), click protection, and attachments.

Domain grouping with aliases is a slightly more complicated topic. You can have as many domains as you want, and it does not affect pricing; only the number of user accounts does (or if you choose other options, listed here).

Basically, first, you have master domains. A master domain can have multiple alias domains tied to it. All email addresses with the first section as the same are aliases of each other in this setup. For example, if domain1.com is a master, and domain2.com is an alias, then me@domain1.com and me@domain2.com are email aliases of each other no matter what. If you wanted to alias “myself” with that same user, then those 2 plus me@domain1.com and me@domain2.com would all be the same user. In this setup, if you wanted me@domain1.com and me@domain2.com as separate users, you would have to split up the domains to not be aliased (in a group). You cannot however alias emails across domains that are not aliased, so for example, if both domain1.com and domain2.com were master domains, you could not alias me@domain1.com and myself@domain2.com. These configuration issues really only tend to be problems with generic names like “info@” and “admin@”, for example, a problem would creep up if me@domain1.com wanted to alias myself@domain2.com but info@domain1.com and info@domain2.com needed to be separate user accounts. If this happened, domain1.com and domain2.com would have to both be their own master domains and myself&me would have to be separate user accounts and the white/black lists would need to be duplicated, and 2 quarantine reports would come in.


I would personally recommend for all normal user inboxes to have high likelihood spam denied, medium likelihood spam as quarantined, and anything with a virus as denied with a return notification. Also, anyone that wanted to not be filtered on a domain that runs through SpamSoap would need to be on one user account as aliases with the no filtering option set. The same goes for users who do not need a quarantine (freeloaders ^_^; ), in which one user account could be set up for basic filtering w/o quarantine and lists.

Because of the no forwarding problem as stated above, all domains would need to be pushed through SpamSoap with emails that needed filtered, and then they could be forwarded afterwards to the appropriate inbox from your own servers. So, in other words, domains that go through SpamSoap cannot be forwarded TO and filtered unless the domains that are forwarding to it are also set up with SpamSoap. The consequences of such are higher likelihood of anything being forwarded being counted as spam and that server being marked as a potential spammer.


SpamSoap also has separate reseller and partner programs for people that forward them business, but they would only be useful if one sent a lot of business their way, generating SpamSoap lots of revenue.


I hope that all made sense, it wasn’t easy to write out x.x; .