Cisco Cisco Email Security Appliance C170 Guia Do Utilizador

This section contains some real world examples of filters with a brief discussion of each.

This filter bounces messages with addresses using 

%

, extra 

@

, and 

!

 characters in email addresses:

user%otherdomain@validdomain

user@otherdomain@validdomain:

domain!user@validdomain

Cisco appliances are not susceptible to these third party relay hacks that are often used to exploit 
traditional Sendmail/Qmail systems. As many of these symbols (for example 

%

) can be part of a perfectly 

legal email address, Cisco appliances will accept these as valid addresses, verify them against the 
configured recipient lists, and pass them on to the next internal server. Cisco appliances do not relay 
these messages to the world.

These filters are put in place to protect users who may have open-source MTAs that are misconfigured 
to allow relay of these types of messages.

You can also configure a listener to handle these types of addresses. See 

 for more information.

[]>

mail3.example.com> commit

Please enter some comments describing your changes:

[]> entered and enabled 3 filters: no_mp3s, mailfrompm, big_messages

sourceRouted: 

if (rcpt-to == "(%|@|!)(.*)@") {

  bounce();

}