SMTPGuard is an anti-spam tool designed for ISPs. It filters out spam before it reaches the user's mailbox, preventing unwanted messages from cluttering up their inbox.
ISPs receive a significant amount of email from their user network, and many emails are unknowingly sent with viruses, inadvertently providing malicious agents with an opportunity to send spam through their servers. This can lead to unexpected spikes in usage and cause SMTP servers to become overwhelmed. With this in mind, SMTPGuard was developed to prevent malicious users from flooding SMTP servers and causing them to become overloaded.
Not only does SMTPGuard prevent overloaded incoming SMTP servers, but also queues SPAM on the outgoing server. However, as the email is often returned to the ISP (perhaps the same server), it causes further pressure on the outgoing server and its queue. To prevent this extreme load, SMTPGuard stops the flood of mails at the gate through the incoming server.
SMTPGuard is point-based, adding points according to the rules file every time a client connects to the SMTP server. It uses information obtained during the SMTP session and then takes actions based on its settings. Remote IP Address, character strings from the MAIL FROM command, and character strings from the RCPT TO command are all used by SMTPGuard. Different actions can be taken based on the settings, ranging from sending an alert email to the administrator to outputting messages to the log.
In the latest release, updates were made to the postfix/flexguard.c file, renaming it to postfix/smtpguard.c. Additionally, there were updates to the postfix/Makefile.am and configure.in files, as well as renaming FLEXGUARD_{CFLAGS,LIBS} to SMTPGUARD_{CFLAGS,LIBS}. The software comes with a detailed README for users to refer to.
Overall, SMTPGuard is a highly effective tool for individuals or ISPs looking to manage their email flow efficiently, prevent malicious users from overloading their SMTP servers, and reduce extreme load in their outgoing server queue.
Version 1.1.1: N/A