Max connections /host

Stephen Swaney steve.swaney at
Wed Mar 29 12:25:16 IST 2006

> -----Original Message-----
> From: mailscanner-bounces at [mailto:mailscanner-
> bounces at] On Behalf Of Tobias Axelsson
> Sent: Wednesday, March 29, 2006 1:41 AM
> To: MailScanner discussion
> Subject: Max connections /host
> Hi
> I know this is little off-topic, but I need to ask someone with good
> knowledge of sendmail :)
> There is a bunch of viruses that connects to sendmail as many times as it
> can and remain the connections until it times out. This can temporary
> cause stop in mail-in. (Running 3 machines that accept 140 connections
> each)
> A good solotions on this could be to set a "Maxconnectionsperhost"-
> variable, but I have'nt found any.
> Please help me all outthere.
> Regards
> Tobias
> postmaster


Take a look at:

Help! My Mail Server Is Being DoSsed!: 

Best site we've found so far that describes:

    1. Limiting the Rate of Incoming Connections
          1.1. The ratecontrol Feature
          1.2. The Connection Rate Throttle
    2. Limiting Simultaneous Connections with the conncontrol Feature
    3. Thwarting Dictionary Attacks
          3.1. Limiting the Number of Recipients per Message
          3.2. Reacting to "Bad" Recipients
    4. Blocking Slammers with the greet_pause Feature
    5. Other Ways to Protect your sendmail Server

Most of these features only work with Sendmail-8.13.x. We've found these
techniques to be very effective.

Hope this helps,


Stephen Swaney
Fort Systems Ltd.
stephen.swaney at

More information about the MailScanner mailing list