Installing and Administering Internet Services

202 Chapter4
Installing and Administering sendmail
Configuring sendmail to Reject Unsolicited Mail
described in this section. Any of these features can be enabled when you
run the gen_cf script, which is distributed with Sendmail.
• Accept Unresolvable Domain
• Accept Unqualified Senders
• Black list Recipients
• Real-time Blackhole List
Accept Unresolvable Domains
This feature enables sendmail to accept all MAIL FROM: parameters that
are not fully qualified. For example, a mail message whose host part of
the argument to the MAIL FROM: parameter cannot be located in the host
name service, such as DNS.
Accept Unqualified Senders
This feature allows you to accept all mail where the sender’s mail
address does not include a domain name.
Normally, the MAIL FROM: commands in the SMTP session will be
refused if the connection is a network connection and the sender address
does not include a domain name.
Blacklist Recipients
This feature enables sendmail to block incoming mail messages destined
for certain recipient user names, hostnames, or addresses. This feature
also restricts you from sending mail messages to addresses with an error
message or REJECT value in the Access Database file.
Example 1
For example, given the following entries in the Access Database file:
badlocaluser 550 Mailbox disabled for this
username
host.mydomain.com 550 That host does not accept mail
[e-mail] 550 Mailbox disabled for this
recipient
Recipient of [e-mail], any user at
host.mydomain.com, and the single address
[e-mail] will not receive mail.