Holes in SMTP blacklists

hcl-bot · November 3, 2006, 4:36am

Hello,

Thanks to the Whitelist new feature, we are trying to use more restrictive Blacklists.

But I notice some “holes” in the SMTP BL filters.

I don’t know if it has begun with R7. Beginning to use bl.spamcop.net, many spams where not stopped with BL.

This means :

all blacklists work well, stopping spam
a large amount of spam is still passing by, despite the fact that they are listed in one or many of the BL (and they are not in my whitelists)

Leaving spamcop, and trying blackholes.five-ten-sg.com, it gets much better but it seems that some spams still go through.

Other BL being used :

Is there any performance issue involved here, any Domino timeout ?

Any idea will be greatly appreciated.

Fabrice

hcl-bot · February 2, 2007, 9:14am

Subject: Holes in SMTP blacklists half-SOLVED

My server was doing every DNS BL lookup twice, spoiling performance.Had to add a trailing dot on each BL name :

zen.spamhaus.org.

For full answer, see :

http://chris-linfoot.net/d6plinks/CWLT-6XAH9Z

http://chris-linfoot.net/d6plinks/CWLT-6XBL4K

hcl-bot · November 3, 2006, 7:01am

Subject: Holes in SMTP blacklists

With only 5 blacklist I don’t think you will experience any problem.

I have experienced some timeouts with at least 16 blacklists.

Timeouts became common with around 32 blacklists in our specific case.

Regards,

J R

hcl-bot · November 8, 2006, 9:07am

Subject: RE: Holes in SMTP blacklists

Tanks for your input.

I suppose that this depends on the machine and the network.

I should do some benchmarking.

Anyway, I tried the INI setting SMTPTimeoutMultiplier=3 and it seems to have resolved the issue. I don’t know if there are any bad side effects coming with this setting.