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Re: [OCLUG-Tech] Mailserver

On Thu, 17 May 2007, ahv [ at ] avantel [ dot ] ca wrote:

> Milter-Greylist with a 20 minute delay
>  - that eliminates a huge number of spam
>  - saves tons of cycles for the next step
> Mailscanner with Clamav and Spamassassin
>  - spamassassin is almost useless for "image" spam
>  - marking an email as spam and forwarding is pointless
> if it's going to another mailserver
> Sendmail is configured to NOT forward mail except for domains I host.
> Several DNS Blacklists (sendmail)
>  - getting less reliable

I am using a similar setup with postfix and finding it quite effective. I 
personally used to get 200-300 spams per day (filtered) and now that's 
down to < 10.

I use greylisting timeout of 6 minutes. That can still cause undeliverable 
mail but appears to cause few, in fact only one that I am aware of lately 
and that I whitelisted.

I see avantel have two mail exchanger addresses. Do these terminate on the 
same host (i.e. with the same rules), or is there a secondary mail system? 
If you are relaying mail from your second MX and it does not implement 
the same rigourous rules as your primary MX then a lot of spam will get 
injected that way (to your secondary).

>  - marking an email as spam and forwarding is pointless

I disagree, depending on what you mean as "marking". I prefer to tag all 
incoming email (I'm handling a number of NGO domains) with SA and let each 
user determine and adjust their filter policy and be accountable to 
themselves for missing emails.

> My system rejects thousands of emails per day through the
> "grey-list", accepts several 100's of emails of which perhaps 30%
> spam.

This seems like a reasonable rejection ratio, in my limited experience. 

Brett


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