Off-Topic: Re: [Mimedefang] Re: DoS Question - Sendmail 8.13 hints

Kevin A. McGrail kmcgrail at
Tue Jan 4 01:41:55 EST 2005

Thanks a lot Sven.  This is some great information below!

I definitely want to look at 8.13.X soon.  Out of interest, do you know if 
you can finally do something like this in the virtusertable?  I know that 
was something they were really looking at but I've been caught up more in 
some of the RBL work for anti-SPAM for the last few months than I planned.

bob.*     error: Nouser No one named bob works here anymore?

Happy New Year,


----- Original Message ----- From: "Sven Willenberger" <sven at>

> Sendmail 8.13.x has new features (and there are patches for 8.12.x) that 
> can throttle such connections. They are:
> A) GreetPause - wherein the server delays the initial response x seconds. 
> Any server that starts sending traffic before this response receieves an 
> error message (designed to stop those trojaned/virus mailservers that 
> blast out spam)\
> B) RateControl - controls how many connections per minute for each unique 
> ip address
> C) ConnControl - controls how many simultaneous connections per given ip 
> address
> These are all controlled via access files and can be configured with 
> defaults and with ip specific exceptions;
> The relevant .mc file entries:
> FEATURE(`greet_pause', `5000')  dnl 5 seconds
> FEATURE(`ratecontrol', `nodelay', `terminate')
> FEATURE(`conncontrol', `nodelay', `terminate')
> example access lines:
> GreetPause:    0
> ClientConn:            0
> ClientConn:             10
> ClientRate:            0
> ClientRate:             15 

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