Hello Sam,

 Thank you for your guide and explanation related to the subject.

 You're right, normally in the case of "550 user unknown" it could generate a 
lot of backscatters. In our case to the outside it doesn't. When the mail 
server gets an SMTP header with bad address, it generates an answer "550 user 
unknown" back to the firewall. The firewall - after getting this error 
message - simply drops the mail, it doesn't generate any mail back to the 
sender. Nothing more happens. (The same procedure takes place when the spam 
filter identifies a spam message and returns with the "550 spam delivering 
disabled" to the firewall -> no backscatter.)

 I tried it from outside, you can do it as well -> try to send a mail to say: 
[EMAIL PROTECTED] and you will not get any answer back. 

 I know in some cases it is not good because the sender will not get any 
response from the accidentally mistyped addressed mails, but on the other 
hand we will not generate a lot of backscatter. 

 I think it's all right, what is your opinion?

 Thanks again for your help and time.

Zsolt Sandor

On Monday 29 May 2006 15:16, Sam Varshavchik wrote:
> SĂĄndor Zsolt writes:
> > Hello Daniel,
> >
> > Thank you very much for the info. I tried to decrease the values, and
> > then completely remarked the routine commands - no sleep at all - and
> > both work fine.
> >
> > Without sleep it is very fast, there were some five thousand bad mail in
> > the queue of the firewall, what were processed and dropped within a few
> > minutes.
>
> Your mail server's speed won't help you when you get blacklisted for
> generating abusive backscatter.



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