In a standard mail server architecture, mail traffic (SMTP) usually arrives at the firewall and is routed directly to your mail server.

By using the Proxmox Mail Gateway, which is implemented between your firewall and the mail server, all mail traffic (SMTP) is first forwarded to the Mail Gateway, all unwanted mails are filtered and deleted or rejected (before queuing filtering), and only then are they forwarded to your mail server.

Receiver Authentication – The Proxmox Solution

Many of the junk messages that reach your network are emails to non-existent users. Proxmox Mail Gateway detects these emails at the SMTP level, which means before they are sent to your networks. This reduces the traffic to be analyzed for spam and viruses by up to 90% and reduces the workload of your mail servers and scanners.

Sender Policy Framework (SPF)

Sender Policy Framework (SPF) is an open standard for validating emails and preventing spoofing of the sender’s IP address. With SPF, the administrator of an Internet domain can indicate which computers are authorized to send emails with a particular domain by creating a specific SPF record in the Domain Name System (DNS).

DNS Based Blackhole List

A DNS-based Blackhole List (DNSBL) is a means by which an Internet site can publish a list of IP addresses in a format that can be easily retrieved by computer programs on the Internet. The technology is built on top of the Domain Name System. DNSBLs are used to publish lists of addresses associated with spam.

SMTP whitelist

Exclude senders from SMTP blocking. To avoid all SMTP checks (Greylisting, Receiver Verification, SPF and RBL) and to accept all emails for analysis in the filtering rule system, you can add the following to this list: Domains (Sender / Recipient), Mail Address (Sender /recipient), regular expression (sender/recipient), IP address (sender), IP network (sender)
Bayesian filter – automatically trained statistical filters
Some specific words are more common in spam emails than in legitimate emails. By being trained to recognize those words, the Bayesian checks each email and adjusts the probability of whether it is a spam word or not in its database. This happens automatically.

Black and white lists

Blacklists and whitelists are an access control mechanism to accept, block or quarantine emails sent to recipients. It allows you to fine-tune the rule system by applying various objects such as domains, email address, regular expression, IP network, LDAP group and others.

Greylisting

Greylisting means that your system temporarily rejects an email from a sender that your system does not recognize. Since transient errors are built into the RFC email delivery specifications, a legitimate server will try to resend the email later. This is an effective method because spammers don’t queue up and try to deliver mail again as a regular Mail Transport Agent would normally do. Greylisting can reduce email traffic by up to 50%. A graylisted email never reaches your mail server, so your mail server will not send useless “Non Delivery Reports” to spammers.

Spam Uri Realtime BlockList (SURBL)

SURBLs are used to detect spam based on the URIs of the message body (usually websites). This sets them apart from most other Real-time Blocklists, as SURBLs are not used to block spam senders. SURBLs allow you to block messages that have spam hosts listed in the message body.

MX records make it easy to set up a high-performance load-balanced mail cluster. You just need to define two MX records with the same priority.

To get started, you need two working Proxmox Mail Gateways, each with its own IP address. Next, you define your MX records. You receive emails on both hosts – more or less load-balanced, using Round-robin scheduling. Round-robin (RR) is a scheduling algorithm that switches between systems. If one host fails, the other is used.

Note: It is always very useful to add reverse lookup entries (PTR records) for those hosts. Many email systems today reject emails from hosts without valid PTR records.

Multiple address records

If you have many domains, it is possible to use one MX record per domain and multiple address records. This way, you can add one DNS MX record to all your domains, which points to multiple IP addresses, eliminating the need to add multiple records to many domains.

Designed as a software application, the strength of Proxmox Mail Gateway is its flexibility. It integrates easily into your existing email architecture and is compatible with any type of mail transfer agent such as MS Exchange, Lotus Domino or Postfix. Or you can use it as a virtual device, directly from the Tuxis Marketplace or on your own infrastructure.