Please note, that some mailservers has a default timeout of 30 seconds for smtp connection. So if you go to delay the HELO/EHLO message for 30 seconds, you will probably block legitimate mails, because the sending server will disconnect, caused by his timeout settings.
Patrick
-----Ursprüngliche Nachricht----- Von: swinog-bounces@lists.swinog.ch [mailto:swinog-bounces@lists.swinog.ch] Im Auftrag von Daniel Kamm Gesendet: Dienstag, 20. Oktober 2009 10:39 An: swinog@swinog.ch Betreff: Re: [swinog] Greylisting
Stanislav Sinyagin wrote:
last AprilMartin Blapp has presented a nice concept at SwiNOG:
instead of greylisting, the SMTP server delays the first OK response to HELO/EHLO for 30 seconds. That is usually enough for the vast majority of spambots to give up.
On a heavy traffic mail server, you probably run into a max session problem when you try to hold many idle connections for 30 seconds.
- Dan
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