Knowledge Base

Protection from Outbound Spam

If your hosting offerings include mail services, keep in mind that your
mail server can be used for malicious purposes, such as sending spam.
Outgoing spam can cause an increased load on the server and complaints
from recipients. What’s more important, your server IP addresses might
be added to public black lists, such as Spamhaus or OpenBL lists.

To prevent spam being sent from your server, Plesk offers a tool that
controls the sending of email messages. This tool gathers statistics
about outgoing messages and prevents mail being sent when specified
limits are exceeded. You can specify limits on outgoing mail at the
following levels: mail server, service plan, subscription,
domain, and mailbox.

Administrators can prevent outgoing spam by using limits on the number
of outgoing email messages per hour. In addition, the administrator can
easily determine the exact source of possible spam with the help of
reports and notifications.

Types of Threats

Plesk introduces different limits for prevention of the following
different types of threats:

Stolen mail accounts.

SMTP user account credentials can be stolen by malicious users when
they hack a mail server by using a system vulnerability (for example,
PHP vulnerability) or an application exploit (for example, exploit
for an outdated WordPress version). Also, if customers use very weak
passwords, their passwords can be obtained by using brute force
tools.

You can prevent this type of threat by limiting the number of
outgoing email messages from a mailbox.
Web scripts for malicious mass mailing.

A malicious user can use a Plesk customer account in order to create
a website with a script that will distribute spam emails. Also, a
malicious user can steal the FTP credentials of a customer account
and upload a website with a mass mailing script via FTP.

You can prevent this type of threat by limiting the number of
outgoing email messages from a domain.
Hacked system accounts on Linux.

Malicious users can gain access to Linux system user accounts by
using system or application exploits. After that, they can plant
scheduled background tasks in crontab. Such scheduled tasks can run
mass mailing scripts that spread spam mail.

You can prevent this type of threat by limiting the number of
outgoing email messages from a subscription.