Your mail server contains important communications like emails and chats that should be secured against the prying eyes of unauthorised individuals as well as against the attacks of malware, adware and viruses, among others. Keep in mind that your efforts towards ensuring a secure mail server will redound to your ultimate benefit in so many ways.
Tip #1 Apply Authentication Steps
POP3 and IMAP connections are not equipped with robust security protocols mainly because these were not originally designed with safety and security in mind. It must be noted that users’ passwords are sent in clear text through the mail server. The result: Your POP and IMAP mail server is highly vulnerable to attacks by hackers and spies, among other individuals with malicious intent on the organisation.
Fortunately, such weakness can be overcome by using the Transport Layer Security (TLS) and Secure Socket Layer (SSL) technologies. These are used in authenticating messages as these emails move across your mail server, thus, significantly lessening the risks for unauthorised usage.
Another method is to set the mail relay options so that the mail server does not become an Open Relay system. Basically, you will set your mail relay parameter such that only the identified domains and IP addresses will receive emails from your server.
Tip #2 Limit Connections
Denial of service (DoS) attack pertains to the flooding of useless traffic to the mail server with the intent of bringing the network to a partial or complete halt. Obviously, DoS attacks like Teardrop and Ping of Death are undertaken by hackers and are made by exploiting the limitation in the email server’s TCP/IP protocols.
To counteract DoS attacks, your mail server administrator can install software fixes to significantly limit, if not completely prevent, the damage. Just remember that new DoS attacks are always possible so your mail server administrator must always be on his toes against these intrusions into an otherwise secure system.
Tip #3 Activate Reverse DNS
Messaging systems like MailEnable use DNS lookups in verifying the existence of the email domain used by the senders before their messages are accepted into the secure mail server. In a similar way, the reverse DNS lookup can deter bogus mail senders and their messages from entering the system.
In the reverse DNS Lookup application, the SMTP verifies that the email sender’s IP address matches both the domain and host names submitted by the client, thus, making it valuable in blocking messages that failed in the matching test from entering the mail server. The command used in the verification is the EHLO/HELO command.
Tip #4 Use Listing Procedures
There are three types of the so-called listing procedures that can be used either as standalone method or in a combination of methods to protect your mail server from attacks. These are:
• End user whitelisting
In a reliable mail server like MailEnable, the system allows for whitelisting as emails and messages arrive through the SMTP. Whitelisting prevents messages from specified domains from being delayed because of greylisting.
• End user blacklisting
In a similar manner, your mail server can be configured to reject messages coming from a given user, domain and/or host at the SMTP level. You must make a list of blacklisted email addresses and domains before the application becomes effective.
Yet another listing procedure in ensuring a secure mail server is greylisting. This aids in lessening spam mail from entering the mail server mainly by delaying messages for a certain period when the sender has not been active in the system for a time. The rationale is that majority of spammers will not try resending their delayed messages but a trusted mail server will continue until the messages come through on the subsequent attempt.
Tip #5 Regular Preventive Measures
Even with all of the abovementioned measures for a secure mail server in place, your efforts will be for naught if and when you let your guard down. You must always perform regular preventive measures in order to keep one step ahead of the hackers, spies and unauthorised users in their plans of bringing your mail server to its knees.