Rejecting incoming emails with blank senders (Sendmail)

[Stephen Swaney]

> -----Original Message-----
> From: MailScanner mailing list [mailto:MAILSCANNER at JISCMAIL.AC.UK] On
> Behalf Of Jason Williams
> Sent: Thursday, December 08, 2005 6:24 PM
> To: MAILSCANNER at JISCMAIL.AC.UK
> Subject: Rejecting incoming emails with blank senders (Sendmail)
> 
> I swear, I just saw this on a recent thread here, but for the life of me,
> I cannot rememeber the name of the thread. So far, I have had much luck
> searcing the archives.
> 
> Im running Sendmail (switching to postfix soon) and I've seen a lot of
> emails today come in with empty sender addresses:
> 
> Dec  8 15:21:04 serenity sm-mta-in[58836]: jB8NL2Mn058836: from=<>,
> size=4633, class=0, nrcpts=1,
> msgid=<20051208225239.C5C345C0A1DA at mwinf3010.me.freeserve.com>,
> proto=ESMTP, daemon=MTA, relay=smtp1.wanadoo.co.uk [193.252.22.158]
> 
> 
> I'm getting really annoyed with this and want to stop it. 9 times out of
> ten,  the recipient is a false address anyways.
> 
> Is there a way to stop this in sendmail? I know you can do it in postfix,
> but im not sure how to do it in Sendmail.
> 
> I appreciate it.
> 
> -Jason

It's seems like I've been answering this question a lot lately :)

It's on the listserv archives. Go to:

http://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=ind04&L=MAILSCANNER&P=R251201&
I=-3&X=7FFD786DDC994945AD&Y=steve.swaney%40fsl.com 

If the link doesn't get you there, search the list archives for a subject
that contains:

	DOS attacked :(

And has a date of Wed, 3 Mar 2004.

Rejecting all e-mail that comes from "From: <>" breaks RFC 1123 and should
only be done in an emergency (read DOS attack). It's not a good idea to do
this on a permanent basis. 

Having said that it looks like over 90% of the email today at many of the
sites we maintain and monitor was Junk; 85%+ spam and 5%+ viruses. Maybe
every day now is a DOS attack :(

Steve

Stephen Swaney
Fort Systems Ltd.
stephen.swaney at fsl.com
www.fsl.com

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