HP-UX Mailing Services Administrator's Guide (B2355-91064)

The following sections discuss the anti-spamming features in detail.
Message Quarantining
Starting with Sendmail, you can quarantine mail messages (envelopes). Queue files or
envelopes are stored but not considered for delivery or display unless the “quarantine”
state of the envelope is undone, or delivery or display of the quarantined items is
requested.
Quarantined messages are tagged using the name hf for the queue file, instead of the
name qf for the queue file, and by adding the quarantine reason to the queue file.
When you enter the following command, the quarantine reason is displayed in a new
line prefixed with QUARANTINE:
mailq -qQ
Where: the-qQ option specifies the quarantined queue items.
Quarantined messages run only when requested with the -qQ option. They do not run
on normal queue displays.
You can run and display restricted mail queues based on the quarantined reason using
the -qQtext option only if the quarantine reason contains the given text. Similarly,
the -q!Qtext runs or displays quarantined items that do not have the given text in
the quarantine reason.
You can use the -qQ flag option to request the delivery or display of quarantined
items. Additionally, you can quarantine or unquarantine messages, which are already
in the queue, using the -Q flag to Sendmail. For example, the following command
quarantines the normal queue items matching the criteria specified by the
-q[!][I R S G][matchstring] option, using the reason given in the -Q flag:
sendmail -Qreason -q[!][I R S G][matchstring]
Similarly, you can use the following command to change the quarantine reason for the
quarantined items matching the criteria specified by the
-q[!][I R S Q][matchstring] option using the reason given on the -Q flag:
sendmail -qQ -Q[reason] -q[!][I R S Q G][matchstring]
If you do not specify a reason, unquarantine the matching items and make them normal
queue items. The -qQ flag informs Sendmail to operate on quarantined items instead
of normal items.
A new error code for the $#error $@ quarantine $: reason, can be used to
quarantine message in check_* (except check_compat) and header check
rulesets. The $: of the mailer triplet is used for the quarantine reason.
Support for Mail Filter (MILTER) APIs
Beginning with Sendmail, you can use the Mail Filter (Milter) APIs to filter all inbound
messages through an external filter program. Milter is designed to enable third-party
82 Configuring and Administering Sendmail