It is critical that a mail server should not operate as an 'open relay', and by default - as installed - Mailtraq will reject open relay attacks
Open relays are when mail servers accept mail that is not for them, and forward it on to the mail servers it should have been sent to. Whilst this may seem the neighborly thing to do, open relays allow spammers to hijack mail servers to send vast quantities of mail and are so 'polluting' that Internet Service Providers will disconnect companies whose mail servers act as open relays.
How to cope with an Open-Relay exploit:
If there has been some misconfiguration or Trojan attack
see how to recover from an open-relay
These are the safe non-open relay settings
This setting is configured on the SMTP Service, Relaying tab.
From the Mailtraq Console, choose Options, Services, then the SMTP service, click Properties, and the Relaying tab.
Set the LAN correctly
Mailtraq uses the LAN setting (explained here) you entered in the Installation Wizard when you installed Mailtraq to know who it is safe to relay. You can confirm those entries by going to Options | Server | LAN and checking they are correct. The LAN definition should be the tightest practical - never use *.*.*.* (meaning 'everybody').
The safe settings are created automatically by Mailtraq, and will look like the following images.
Most installations do not require changes to these settings.
If you have made changes to your SMTP service settings you can use these pictures as a reference.
The SMTP Service dialog is
accessed from the Console
Services | Properties
should be set to
'Allow any client to connect'
These settings are
empty by default.
'Relay for non-local senders'
is normally enabled*.
Black Lists tab gives access
to both Black & White lists.
Read more here ...
How to check
There are a number of web resources that will run live checks on your Mailtraq to make sure you are not an Open Relay.
* What this means more fully is: Relay for non-local senders inside this LAN
This allows anyone who is within the IP range that you have defined as local (see Firewall) to send mail using a domain name that isn't defined as being a local domain (within Mailtraq).
Full details of the settings necessary to allow relaying when required are provided at the [Help] button in the service dialog.
KB01080201 Preventing Mail Relay Abuse (Technical background)
Web resources - to check your configuration Read more ...