Essential Aspects of Securing a Mail Server

Jul 28,2021 by Manoj Yadav

Protecting your mailing infrastructure is a prerequisite for building long lasting customer relationships. It is a well established fact that secured mailing infrastructure is closely associated with sender’s image and goes a long way to establish a sound reputation. One must ensure that the email system is capable of blocking entry of spam to avoid potential threats.

Possible hazards of spam

Spam can find an easy entry into the inbox of your subscribers and can pose a large array of threats including creation of large number of complaints against IP addresses and domains. Your legitimate mail can also be hampered in terms of subscriber engagement due to presence of spam.

Spam can cause your Mail Box Provider as well as subscribers to block your mail. Spam traps can be implemented by directing spam to random email accounts that are not included as your subscribers. Your mail is prone to be blacklisted in the event of an unauthorized content originating from your mail and getting into spam traps.

The above mentioned issues need to be seriously looked at because leading Mail Box Providers are constantly assessing security and performance parameters for arriving at filtering decisions that would restrict connections from your mail server infrastructure.

It needs to be noted that no matter how much time it takes to normalize performance metrics, your ROI and email deliverability is bound to suffer significantly. In order to protect your mail server one should adopt the tips mentioned below.

Security through encryption – This is probably the most significant step to make sure that the connections are secured properly You may use SSL or TLS to encrypt IMAP and POP3. It should be noted that POP3 and IMAP connections were not created to have safety features in the first place. This explains why these are usually utilized without proper authentication. Since transmission of passwords is executed in clear text via your mail server, this can lead to a significant vulnerability of by providing open access to spammers and hackers. In order to execute strong authentication, SSL/TLS is the most reliable and sought after way.

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Implementation of mail relay configuration – It is always better not to become an open relay for spammers by configuring the mail relay parameter as very restrictive. This option is provided by all email hosting servers and needs you to setup relay instructions by specifying domains and IP addresses that would be used for sending mails. To put it simply, the option aims at verifying delivery destinations that need to be strictly followed by SMTP protocol. This needs to be carefully configured because any wrong configuration may lead to misuse of your network resources and mail server to spam others thus exposing you to get blacklisted.

Restriction of connections for security against DoS attacks – By limiting connections and authentication errors to SMTP server, you can prevent DoS attacks. You need to get rid of unnecessary server functionalities by way of disablement of such default settings. Vital parameters required to e used for managing connection limits are number of total connections, total number of concurrent connections, and rate of maximum connections. The parameters depend upon hardware specs of server such as CPU, memory, and NIC bandwidth. It may require refinement over time for maintaining optimal values of vital parameters. You may also have a dedicated mail server to shift services including FTP and so forth. The total, maximum, and simultaneous connections to SMTP server should be limited.

Implementation of access control mechanism – You can certainly secure your server from any unauthorized access or intrusion by implementing access control through authentication. Users need to enter username and password to use server for sending mail in case of SMTP authentication. Do not credentials for share server access with several people and such access should only be granted on SOS basis.

Prevention of abuse – Since DNSBL servers consist of list of all known spammer domains and IPs, you need to assess DNSBLs (DNS based Black Lists) to execute rejection of emails originating from IPs or domains listed therein. Ideally one should use maximum possible numbers of DNSBL servers. Additionally you can also verify SURBL (Spam URI Real Time Block-lists) to reject messages that may contain malicious and invalid links. You can also prevent malicious intrusion attempts by employing outbound filtering with your web forms such as CAPTCHA.

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Significance of securing mail server

Maintaining seamless security of your mail server is a vital aspect of implementing a successful email campaign. It is also essential for making optimum use of the Certification program. There are number of other advantages such as enhanced deliverability of emails at important MBP, avoiding sensitive MBP filters, active links, and unblocking of images. It should be remembered well that spam detection on your mail by compliance team may result in suspension of domain or IP addresses from the Certification program

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