SUF's Blog

Get Transport Rules into work to stop SPAM

suf@freemail.hu — Mon, 11 May 2009 14:10:00 GMT

A few days ago I've got a question:

How can I block the messages with empty from address in the Exchange 2007.

The trivial answer is:

By using the Sender Filter Agent on the Edge Transport can block the empty senders.

But...

Stop here for a moment. It will block the messages with empty address in the MAIL FROM: smtp command. What will happen with the messages what has no From: address in the message header. The Sender Filter will not even know about these messages because it just examines the smtp communication not the message contents.

The solution:

We are able to write a Transport Rule (running on the Edge or the Hub Transport) what able to block such message:

$Condition = Get-TransportRulePredicate FromScope
$Condition.Scope = 'NotInOrganization'
$Exception = Get-TransportRulePredicate FromAddressMatches
$Exception.Patterns = @("@")
$Action = Get-TransportRuleAction DeleteMessage
New-TransportRule -Name "Remove message with empty from address" -Conditions $Condition -Exception $Exception -Actions $Action

You may realize that I used a single @ to determine the empty sender. You can change it to real e-mail regex pattern if you want to validate the e-mail address format. In that case all messages with not valid format sender will be dropped.

MVP

suf@freemail.hu — Mon, 30 Mar 2009 11:41:00 GMT

I just got the news. I was not reelected as MVP so removed the MVP logo from the site.

DistList new build

suf@freemail.hu — Wed, 18 Feb 2009 13:13:00 GMT

I've made a slight modification in the handling of the subject tagging. The new version (DistList v1.2b5 & DistList 2007 v2.1b4) allows to switch on and off the subject tagging on the distribution groups individually.

Download links:

DistList (Exchange 2003 version)

DistList 2007 (Exchange 2007 version)

Documentation

Source code

DistList & DistList 2007

suf@freemail.hu — Fri, 06 Feb 2009 11:02:00 GMT

Two years ago I was writing an Exchange 2003 SMTP Sink and an Exchange 2007 Transport Agent what able to switch an Exchange distribution list to a mailing list. This software was never published before because I'd no time to clean up the code and write proper documentation to it.

Now I'd time to finish this work so here thay are:

DistList (Exchange 2003 version)

DistList 2007 (Exchange 2007 version)

Documentation

Source code

ClamAgent - Plans 2.

suf@freemail.hu — Fri, 12 Dec 2008 06:36:00 GMT

I've got few comments, responses on the first release (to be exact, two comments). The first was asking for the Exchange 2003/IIS SMTP version, the second realized some configuration issues where the agent continuously throwing exceptions...

More...

ClamAgent - Plans

suf@freemail.hu — Thu, 04 Dec 2008 09:09:00 GMT

What will be the future of the ClamAgent

More...

First English blog entry

suf@freemail.hu — Thu, 04 Dec 2008 08:56:00 GMT

Wellcome to my English blog...

More...

Alias and Autoforward handling for Windows Server 2003 POP3 Service

suf@freemail.hu — Sun, 28 Aug 2005 23:00:00 GMT

[04/03/2009] This article was written long time ago (as you see in the date) to my original web site http://www.gomori.hu. Because I will use this site further for family purposes only I'm migrating the IT related articles out.

I tried to deploy Microsoft Windows Server 2003 POP3 Service, but I've realized lack of two important (at least it important to me) features. These are the Autoforward and the mail Alias (the ability to add more than one e-mail address to a single mailbox). Because I needed these functions for the deployment I wrote a script witch add them to the POP3/SMTP service.
I implemented the functions as SMTP Event Sink in JScript.
It uses an Access database (Microsoft Jet engine) to store the data required for the implementation. The database has two tables:
Alias Table:

Column	Data
ID	An autoincrement id field. Not used in this implementation.
Alias	The alias address.
Mail	The original mail address.

Forward Table:

Column	Data
ID	An autoincrement id field. Not used in this implementation.
Mail	The original mail address.
Forward	Forward address(es). Multiple addresses allowed
KeepOriginal	Determine if the mail have to delivered to the original mailbox or not.

All e-mail fields need to be in SMTP:name@domain format. Where multiple addresses allowed, it must be separated with semicolon.
In the script code you must change the the DBfile variable's value to the full path name to the location of the database file used.
Registration: The registration procedure involve the same procedure as any other SMTP OnArrival Event Sink. The exact commands looks like the following:

cscript smtpreg.vbs /add 1 OnArrival
	Pop3Helper CDO.SS_SMTPOnArrivalSink "mail from=*"
cscript smtpreg.vbs /setprop 1 OnArrival
	Pop3Helper Sink ScriptName "c:\Scripts\SMTP\pop3.js"

Fortunately with this solution you don't need to create a second SMTP Virtual Server and route all messages thru it because the message is always in MIME format witch means no MAPI/MIME conversion involved.
Finally here is the script code can be downloaded here.