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SMTP Gateway Overview
Mailshell's Anti-Spam Gateway is an SMTP
proxy that plugs in anywhere along an SMTP chain. The proxy
listens for messages from an incoming SMTP port and then
forwards messages downstream to another SMTP Mail Transfer
Agent (MTA). The proxy scores each message and inserts a
header, X- SpamCatcher-Score, indicating a 'spam score'
for the message.
X-SpamCatcher-Score Header
The Mailshell Anti-Spam score indicates the probability
that a message is spam. The higher the number, the more
likely a message is spam. Mailshell Anti-Spam scores range between
0 and 100.
X-SpamCatcher-IP Header
This header contains the IP address of the
sending MTA. The information is used for IP Blacklist checks.
Since the SMTP Gateway is plugged in between the sending
and the receiving MTA, the header information is the only
way that the receiving MTA can identify the sending MTA's
IP address.
Destination SMTP Servers
The SMTP Gateway will 'round robin' from a
list of Destination SMTP servers.
Specify the server and port number of the
destination SMTP servers in the Preferences tab of the Admin
Console. The server can either be a hostname or an IP address.
The port number should always be numeric. If a port number
is not specified, the default port of 25 is assumed.
Global Approved List
The SMTP Gateway will accept a list of sender
addresses or domains whose messages never will be considered
spam. For these messages, the X- SpamCatcher-Score header
will always be 0.
- Add an approved sender
To add an Approved Sender, click on the Approved Senders
tab; then select the Add button. Enter the sender into
the field provided, then click the OK button. You can
specify either an email address (e.g., joe@yahoo.com)
or a domain (e.g., yahoo.com). If you specify a domain,
any address sending from that domain will be approved.
- Edit an approved
sender
To edit an Approved Sender from your list, click on the
Approved Senders tab; then select the address or domain
you want to edit and click the Edit button. Edit the sender
in the field provided, then click the OK button.
- Delete an approved
sender
To remove an Approved Sender from your list, click on
the Approved Senders tab; then select the address or domain
you no longer want to approve and click the Delete button.
Mail from this address or domain will no longer automatically
be approved.
- Import approved senders
list
You can import multiple approved senders by importing
a text file, which contains a list of approved senders,
one email address or domain per line. To import an Approved
Sender list, click on the Approved Senders tab; then click
the Import button. Select the file you want to import
in the pop-up window, and then click the Open button.
- Export approved senders
list
To export an Approved Sender list, click on the Approved
Senders tab; then click the Export button. Enter a name
for the file you want to export in the pop-up window,
then click the Save button.
Global Blocked List
The SMTP Gateway will accept a list of sender
addresses or domains whose messages are always considered
spam. For these messages, the X- SpamCatcher-Score header
will always be 100.
- Add a blocked sender
To add a Blocked Sender, click on the Blocked Senders
tab; then select the Add button. Enter the sender into
the field provided, and then click the OK button. You
can specify either an email address (e.g., joe@yahoo.com)
or a domain (e.g., yahoo.com). If you specify a domain,
any address sending from that domain will be blocked.
- Edit a blocked sender
To edit a Blocked Sender from your list, click on the
Blocked Senders tab; then select the address or domain
you want to edit and click the Edit button. Edit the sender
in the field provided, and then click the OK button.
- Delete a blocked
sender
To remove a Blocked Sender from your list, click on the
Blocked Senders tab; then select the address or domain
you no longer want to block and click the Delete button.
Mail from this address or domain will no longer automatically
be blocked.
- Import blocked senders
list
You can import multiple blocked senders by importing a
text file, which contains a list of blocked senders, one
email address or domain per line. To import an Approved
Sender list, click on the Approved Senders tab; then click
the Import button. Select the file you want to import
in the pop-up window, and then click the Open button.
- Export blocked senders
list
To export a Blocked Sender list, click on the Blocked
Senders tab; then click the Export button. Enter a name
for the file you want to export in the pop-up window,
then click the Save button.
Precedence of Approved and Blocked Addresses
When an address matches entries in both the
Global Approved and Global Blocked lists, the following
priority will be observed. Email addresses will take precedence
over domains, e.g. if you block the domain host.net but
approve the specific address joe@host.net, mail from the
latter sender will be approved. In addition, approved addresses
will take precedence over blocked addresses if identical
entries exist on both the Global Approved and Global Blocked
lists.
Logs
Mailshell Anti-Spam logs via the Event Log.
Mailshell Anti-Spam Network Settings
It is possible to configure several general
settings for the SMTP Gateway. You can either run \Admin.exe
or directly edit the control file which is located at \conf\spamcatcher.conf
and can contain the following settings:
- Rule Update Frequency
You can configure Mailshell Anti-Spam to automatically check for
updated spam rules.
Default: If this entry is missing or misconfigured,
the default will be to check for rule updates every 60
minutes.
- SpamCatcher Network
Checks
You can configure Mailshell Anti-Spam to check message fingerprints
against the Mailshell database of known spam.
Default: If this entry is missing or misconfigured,
the default will be Yes.
- Spam Threshold for
rejecting messages
You can configure Mailshell Anti-Spam to delete all messages that
have a Mailshell Anti-Spam score above a certain level. Mailshell Anti-Spam
scores range between 0 and 100. The higher the number,
the more likely a message is spam.
Default: If this entry is missing or misconfigured,
the default will be 100.
- Timeout for spam
check
You can configure Mailshell Anti-Spam to stop spam scoring if
it takes too long. Timeouts happen on a message-by- message
basis. Those messages that timeout will have a X-Spamcatcher-Score
header based solely on the spam rules.
Default: If this entry is missing or misconfigured,
the default will be 5 seconds.
System Requirements
Windows 2000/XP
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