The presence of anti-spam and security features on an effective and efficient professional mail server like MailEnable cannot be overlooked. Keep in mind that spam can quickly fill inboxes with useless emails, steal information from databases, and affect server functionality, among other adverse effects. Basically, the more effective and efficient anti-spam and security protocols in a professional email server, the better it will be for the organisation in general and for its employees in particular.
Although there are many anti-spam features available in the market, the following are the most important features that every business, large and small, should have on its enterprise mail server.
#1 Bayesian Filtering
Think of the Bayesian spam filter as the intelligent anti-spam feature in the best professional mail server. Bayesian filtering works by calculating the probability of an incoming email as spam based on its contents such as:
• words and characters in the senders, message paths, body and headings of the email
• Meta information
• pairs of words and phrases
• other aspects like HTML codes
Even the entire context of the email will be rated! The filter gradually builds up a virtual library of the components of valid email and spam email by “learning” so much so that little to no spam can get through the professional email server in due time.
#2 Reverse DNS Blacklisting
This anti-spam filter method involves the use of a DNS-based Blackhole List (DNSBL), which is a list of IP addresses published via the Internet Domain Name Service (DNS) identified as networks, sites and computers associated with spam email. Basically, the professional mail server must be configured to either flag or reject messages sent from sites listed on the blackhole list.
Keep in mind that the DNSBL is not a specific policy or a specific list – it is a software mechanism with dozens in existence, each one using a wide variety of criteria in listing and delisting IP addresses. You must then review the capabilities of DNSBL providers in terms of their ability to match your requirements in the anti-spam filter.
#3 End User Blacklisting And Whitelisting
Think of blacklisting and whitelisting as the opposite ends of the spectrum but both have similar function – to block out spam from entering the system, thus, protecting its integrity from the likes of phishing attacks. Experts are divided on the issue of blacklisting and whitelisting particularly on the pros and cons for each method. The best solution: To include both anti-spam methods in a professional mail server like MailEnable, thus, allowing clients to enjoy the best of both types.
Basically, email senders on the blacklist will immediately be refused transmission of their messages to the intended recipient, a process facilitated by the SMTP connector. Emails from whitelisted addresses are delivered as soon as possible – no delays by greylisting – to the intended recipient via SMTP as well.
#4 Abuse Prevention
Many email senders, however, abuse their privileges to the detriment of the organisation/recipient. The anti-spam filter that prevents such abuses involves the administrator setting limits to the number of messages sent by certain users. A professional mail server like MailEnable, for example, has default settings of 100 messages per hour sent through the system, thus, preventing the abuse of privileges.
But that’s not all. The best enterprise mail server can also be programmed to permanently block IP addresses that have issued one too many invalid commands, or provided one too many invalid passwords, or violated one too many security policies. Limits are also imposed on these anti-spam measures.
Sender Policy Framework (SPF)
This anti-spam filter in a professional mail server works by discouraging spam mailers to hide behind the practice of email spoofing to enter the email server. Basically, the Sender Policy Framework (SPF) specification will define a policy framework coupled with an authentication scheme and a machine-readable language that will identify valid email senders from spam mailers using a query searching method.
When all of these anti-spam methods – and perhaps a few more like relay control, antivirus scanning and message filtering – are in a professional mail server, then you have made the right choice.