This article covers how to locate the mail spammer in a Plesk server which is a bit difficult when compared to #Cpanel servers.
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 in Plesk:
Plesk introduces different limits for prevention of the following different types of threats:
1. 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by using a system vulnerability (for example, PHP vulnerability) or an application exploit (for example, exploit for an outdated WordPress version).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.
2. 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.
3. 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.
Best practices for sending outgoing mail from a #Plesk server:
1. Configure the #hostname for a Plesk server
Go to Tools & Settings > Server Settings and type in your server's hostname.
2. Enable SPF/DKIM/DMARC features
By default, a SPF DNS record is added to the domain's DNS zone during a domain creation, if this DNS record exists in the Plesk DNS Template.
Make sure there is a TXT record for SPF in domain's DNS settings at Domains > example.com > DNS Settings
3. Make sure that DKIM support is enabled server-wide in Plesk at Tools & Settings > Mail Server Settings.
4. A reverse DNS (rDNS) lookup returns the hostname of an IP address. Many mailbox providers, including Gmail and Yahoo!, will block email coming from a mail server that does not have rDNS in place.
To configure rDNS, a PTR DNS record should be created by the owner of the IP address.
Contact your hosting service provider or Internet Service Provider (ISP) to get more details.