Using this facility, MAILsweeper can be configured to:
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For more details on spamming and spoofing and the other methods MAILsweeper uses to provide protection from such mail, see page 5-9 and page 5-15 respectively. |
To control access to your mail router, double click on the MAILsweeper Console icon, found in the Control Panel.
This displays the MAILsweeper dialog box, showing several tabs.
Click on the Misc tab to access the required options.
Access to your mail router is controlled by three fields on this dialog box:
The first field can be used to specify known hosts from which all mail should be blocked, for example, those known to supply spam mail. The remaining two can be used in combination to prevent mail spoofing, by selectively restricting mail relay. This will prevent remote hosts from distributing mail to other remote hosts via your mail router.
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The Insert Status header in POP3 mail check box, Enable full VRFY support check box and Address Rewriting area are not currently used but are in place for future releases. |
The information contained in these fields is subject to certain conditions, as explained below.
Reject all incoming mail from these hosts specifies a list of hosts from which all mail should be rejected outright. For mail rejected by this field, the information in the other two fields does not apply.
For mail that has not been rejected by the first field, Accept mail for relay from these hosts specifies a list of hosts that are granted full use of the mail router to deliver their mail. If a host is not in this list mail will still be accepted, but only if the destination mail domain is listed in Accept mail for relay to these domains.
This is summarised on the following diagram and explained in more detail on the following pages:
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Reject all incoming mail from these hosts: - This field specifies a list of hosts from which all mail is rejected outright.
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This is a very powerful feature and should only be used to block mail originators of junk mail as a last resort. |
This field can contain a comma-separated list of host names or IP addresses, optionally containing the wildcard character *. Precede a host name with an exclamation mark to indicate that matching hosts are an exception and should be excluded from the rejected list.
The list of host names in this field is checked from left to right, so if you list a host preceded with an exclamation mark, that is, as an exception, it should always appear first.
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It is important to ensure that the correct ordering of host names is used in this field, due to the order in which checking is performed. |
Using this example, mail arriving from all hosts matching *example.com is rejected, unless it arrives from the host exception.example.com. Incoming mail from all other sources is accepted.
By default this field is blank, meaning no mail is rejected.
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If host names are specified in this field, as opposed to IP addresses, then the Look up SMTP hosts box must be checked. |
Accept mail for relay from these hosts: - This field only applies to mail that has not already been rejected by Reject all incoming mail from these hosts.
This field can contain a comma-separated list of host names or IP addresses, optionally containing the wildcard character *. Precede a host name with an exclamation mark to indicate that matching hosts are an exception and don't belong in the accepted list.
The list of host names in this field is checked from left to right, so if you list a host preceded with an exclamation mark, that is, as an exception, it should always appear first. See the previous page for an example.
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If host names are specified in this field, as opposed to IP addresses, then the Look up SMTP hosts box must be checked. |
By default this field contains *, meaning mail from all hosts is accepted. In this case, the list of domain names in Accept mail for relay to these domains can be ignored.
Accept mail for relay to these domains: - This field only applies to messages that have not already been rejected by Reject all incoming mail from these hosts and have not been accepted by Accept mail for relay from these hosts. It specifies mail domain names to which mail will be accepted. If the recipients' domain name is not in the list, the mail will be rejected, although if the mail has more than one intended recipient it may be allowed through for other recipients.
This field can contain a comma-separated list of mail domain names, optionally containing the wildcard character *. Precede a domain name with an exclamation mark to indicate that matching domains are an exception and don't belong in the accepted list.
The list of domains in this field is checked from left to right, so if you list a domain name preceded with an exclamation mark, that is, as an exception, it should always appear first. See page 2-64 for an example.
By default this field is blank and will never apply because the default for the Accept mail for relay from these hosts field is *.
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If the default setting for Accept mail for relay from these hosts is changed, this field must include your local domain names, otherwise all mail for your local domains will be rejected. |
It is important to remember that MAILsweeper acts as a mail relay. For this reason, by using:
This enables MAILsweeper to send and receive mail normally, while ensuring it is not redistributing other peoples mail. That is, it prevents MAILsweeper from being used as a relay by remote hosts. This is an effective guard against spoofing, the process by which remote mail users can relay mail via your mail router, such that it appears to originate from you. See page 5-15 for more details.
Some example configurations are shown below:
Reject all incoming mail from these hosts: server.spam.com, *junk.com.
Accept mail for relay from these hosts: *
Accept mail for relay to these domains:
This example causes all mail that arrives from the host server.spam.com and all hosts that match *junk.com to be rejected.
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This example still allows full mail relaying to occur. It is recommended that you configure MAILsweeper so as to selectively restrict relaying. Some examples are shown below. |
Relay prevention (permanent Internet connection):
Reject all incoming mail from these hosts:
Accept mail for relay from these hosts: server.mycom.com
Accept mail for relay to these domains: *mycom.com
In this example, mail is only accepted if it is from server.mycom.com, that is you own mail server, or if it is destined for a domain that matches *mycom.com, that is, your own internal domains.
Relay prevention (mail received via ISP):
Reject all incoming mail from these hosts: !*mycom.com,!*myisp.com,*
Accept mail for relay from these hosts: *
Accept mail for relay to these domains:
In this example, all mail (*) is rejected unless it arrived from a host that matches *mycom.com or *myisp.com, that is, from within the local company or from the ISP. Note that the exceptions are listed first.
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