Spamblocker and Fetchmail OK?

OliverScott

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Not sure if this should go here on in the general email forum...

I am currently not using spamblocker but am using various dnsbls for spamassassin scoring which works OK but is fairly high on resource usage.

I am considering blocking some email on delivery using spamblocker (now I have a good idea of the relative accuracy of the various services) but have one concern:

I have several email accounts which are collected by the server using fetchmail (from a pop box on another server) rather than being delivered directly by smtp. Does this matter? Emails collected by fetchmail are passed through exim so will spamblocker do anything with this email or will it only see the last (local) server address which should not be blacklisted! If it does find somthing it doesn't like what would happen to the email, as it can't be refused as normal can it?

The one thing stopping me from just trying it to see what happens is that the last thing I want to do is to bounce messages back to a forged address and become a spammer myself!

Any help greatly appreciated :)
 

nobaloney

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I have several email accounts which are collected by the server using fetchmail (from a pop box on another server) rather than being delivered directly by smtp.
Yes it matters, since SpamBlocker blocks only based on server reputation, it will block based on the reputation of the server sending it the email. I believe in your case that'll be localhost. It shouldn't block localhost.
Does this matter? Emails collected by fetchmail are passed through exim so will spamblocker do anything with this email or will it only see the last (local) server address which should not be blacklisted!
Yes.
If it does find somthing it doesn't like what would happen to the email, as it can't be refused as normal can it?
It won't find it.
The one thing stopping me from just trying it to see what happens is that the last thing I want to do is to bounce messages back to a forged address and become a spammer myself!
And that's a good thing ;) .

Jeff
 

OliverScott

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Many thanks for the quick reply!

One final question (which you many or may not be able to assist with):

What would happen to emails that are collected using fetchmail and are caught by ClamAV as part of the exim process?

Thanks!
 

nobaloney

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I don't have any idea (though I probably should). I know they won't be returned anywhere because exim tries only to block them. I still don't know how fetchmail injects the email into exim. Do you?

Have you tried this to see? Maybe you can tell us :) .

Jeff
 

OliverScott

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I don't have any idea (though I probably should). I know they won't be returned anywhere because exim tries only to block them. I still don't know how fetchmail injects the email into exim. Do you?

Have you tried this to see? Maybe you can tell us :) .

Jeff
Fair comment! Will look into it and run some tests - watch this space...
 

OliverScott

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OK - I have read the manual and tried various things on my server and am ready to report!

If fetchmail is configured to deliver an email to a non-existant account or if the message is refused due to containing a virus or being spam etc then the following will happen by default (with current versions of fetchmail):

A warning email is sent from FETCHMAIL-DAEMON@'TheServerFetchmailRunsOn' to root@'TheServerFetchmailRunsOn' which states that the message could not be delivered and which has the original message attached to it.

This action can be changed by using an 'antispam' option which simply discards the email, or by specifying a 'spambounce' option which sends the email back to the originating email address (which was probably fake). This second option is NOT recommended.

There is one potential problem with this, in that the failure message which fetchmail sends to root could also be blocked due to containing a virus! In this case I am not entirely sure what happens to the message (I think it is simply discarded), but there was a bug in older versions of fetchmail which could cause it to crash in this scenario...

Details of this bug are here, as well as the versions affected:

http://fetchmail.berlios.de/fetchmail-SA-2007-02.txt
 

nobaloney

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Thanks for the report; it took me a long time to respond because I was on vacation.

Have you tested that virus scenario?

DA's default install of exim won't accept root email; you'll have to forward it to a different address.

If you're using SpamBlocker3 beta you can put that domain into the skip_av_domains file. Or you can Set up an address similar to my "errors@" address, and change the exim.conf file to manage that.

Once you've done it and tested it :) let me know, and I'll make the necessary changes to the SpamBlocker3 before the final release.

Thanks!

Jeff
 
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