Technical data

Configuring and Managing SMTP
17.6 Configuring SMTP AntiSPAM
17.6.7 Blocking Mail from Specified Senders
You configure SMTP to reject mail based on the address of the sender. The
sender’s address is specified in the MAIL FROM command. (The terms ‘‘sender
address’’ and ‘‘MAIL FROM address’’ are synonymous.) To specify sender
addresses from whom mail will always be rejected, include the Reject-Mail-From
list in the SMTP.CONFIG file.
The Reject-Mail-From list includes wildcarded patterns that are checked against
the sender address. If the SMTP server matches the sender address against a
pattern in the Reject-Mail_From list, the MAIL FROM command is rejected and
the link is disconnected. Wildcarded patterns may include the standard asterisk
(*) and percent sign (%) wildcard characters.
For example:
Reject-Mail-From: *.xyz.com, known.spammer@*, *the_internet*
To specify hosts from which to allow mail, even if the address matches that
specified in the Reject-Mail-From list, include them in the Accept-Mail-From list
in SMTP.CONFIG.
The Accept-Mail-From list includes wildcarded patterns that are checked against
the sender address. If the SMTP server finds that the MAIL FROM address
matches an entry in the Reject-Mail-From list, it then checks the Accept-Mail-
From list also. You can use this list to allow mail from legitimate senders in the
domains listed in the Reject-Mail-From list.
For example:
Accept-Mail-From: *@notabadguy.xyz.com, [e-mail]
In this example, the entry [e-mail] allows mail
from the sender address [e-mail] , even though it
matches the entry *the_internet* from the Reject-Mail-From list. Likewise, it
accepts mail from [e-mail] , even though it matches the entry
*.xyz.com in the Reject-Mail-From list.
In addition to the Accept-Mail-From list, you can specify the following
configuration options in SMTP.CONFIG to allow mail from senders in the
Reject-Mail-From list:
• Accept-Unqualified-Senders
By default, if the TCP/IP Services SMTP server receives a message with an
unqualified sender address, or with a sender address with no domain at all, it
will reject the MAIL FROM command and disconnect the link.
For example, the following sender addresses would be rejected by default:
MAIL FROM:<somebody>
MAIL FROM:<somebody@someplace>
The first address has no domain and the second has an unqualified domain.
To accept mail with these types of sender addresses, set Accept-Unqualified-
Senders in SMTP.CONFIG, as follows:
Accept-Unqualified-Senders: TRUE
When the Accept-Unqualified-Senders option is set, the SMTP server does not
check whether the sender address either has a domain or is fully qualified.
• Accept-Unresolvable-Domains
17–24 Configuring and Managing SMTP