Top 7 Tips To Protect Your Email Server From Hackers


On any given day, an average office worked receives 121 emails. That works out to 15 emails for every working hour. Now multiply that number with the number of workers in an entire organization. Such a mind-boggling number.

All these emails are not random exchange of pleasantries, instead, most of them contain sensitive information about business proposals, strategic documents, financial metrics and several such information. Such information if made public can ruin the business and shake the confidentiality of its stakeholders.

That said, your email server needs all bells and whistles to stay secure on the web. It must be armored with a shield that will end off all possible hacking attempts.

How to do that? In what is to follow, we explain some simple ways to secure your email server.

#1 Apply Authentication Steps

Traditionally, email servers use POP3 or IMAP protocols which have security vulnerabilities. They were primarily designed to help store data on the email server. Security was never the primary priority in their design process. It is worth noting that passwords are sent as plain texts through these servers, which is nothing but dangerous for any organization.

How to secure these POP3 or IMAP protocols? Apply authentication steps using HTTPS encryption. An SSL Certificate for exchange server or other email servers scrambles the data exchanged between the email and the server ensuring total security of passwords or other sensitive information being exchanged. The authentication ensures that the data exchanged by the server as well as the requests processed by it does not suffer any data leakage or interception from external sources.

#2 Limit the number of connections

Having too many server connections can pave way to DDoS attacks. DDoS attacks work by raising a flood of requests by bots or crawlers. The traffic request is so heavy that it freezes the server preventing users from using the email service. The consequence of the email server shutting down for the business can be disastrous. From failing to provide customer support to missing client responses, it can cost quite a fortune.

Limiting the number of connections help prevent DDoS attacks.

Limiting the number of connections your email server and keeping the errors that it can accommodate to an optimal level can reduce the chances of DDoS attacks. Also, do a thorough check of your SMTP server and remove any unnecessary default settings that hackers can exploit to find their way in.

#3 Use Digital Signatures for emails

Identity theft is one of the serious dangers of compromised email servers. If there is an option for anybody on the Internet to send, receive or intercept an email, you are bound to suffer several losses including financial loss.

To avoid identity theft through emails, use Digital Signatures. Digital Signatures have been long since recognized as a best practice to ensure user authenticity and data integrity in email communication. A Digital Signature is a bit sized file which is used to establish the veracity of a document’s contents and also the user’s identity.

Users who want to access your emails can use the public key of the Digital Signature and be assured that it is indeed you who has sent the message and not any imposter who has access to your email id.

#4 Monitor requests from DNS-based blacklists

DNS-based blacklists (DNSBL), also known as real-time Blackhole list (RBL) is an effective to keep spam emails and email-server threats at bay. It is a collection of IPs from which emails spams have originated in the past. Cross Check the list and verify if your website is receiving any requests.

If you do, reject them or mark them as malicious links. Web firewall tools like Amazon WAF help monitor and safeguard your servers including email servers from such malicious requests. There are also other tools like MailEnable which check for the sender’s veracity before accepting message is allowed inside the email server.

#5 Listing procedures

Apart from monitoring requests, there are listing procedures which help protect your email server from attacks. You can choose from:

  • End user whitelisting
  • End user blacklisting
  • Greylisting

You can use either of these as a single strategy or mix and combine them to create a total secure system for your email server. In the first one, end user whitelisting, the mail server allows requests from DNS that are already recognized as safe.

In Blacklisting, it does the exact opposite of rejecting requests that come unknown or potentially unsafe email addresses.

In Greylisting, the mail delivery is delayed until a certain time to see if it qualifies as spam or just another mail which has the traits of a spam mail, be it in content or context.

#6 Enact SPF to eliminate malicious mailers

SPF which stands for Sender Policy Framework has become popular among system admins and email server managers. It checks the authenticity of the sender address before the mail is granted access to the email server. If the SPF traces that the email sender is a fake address or one that can possibly damage the server, it prevents access immediately thus saving the entire server from any possible damage.

#7 Use a spam filter

Do you know? On a test that Mcafee conducted, more than 97% of users were unable to distinguish a phishing mail from a legitimate mail. Setting a spam mail filter at the server level and for users is a good way to prevent users from preventing their data voluntarily to scammers. The scam filter ensures that emails which do qualify to be genuine mails are directed to the spam folder which are eventually deleted by the user.


These are some ways how you can secure your email server and ensure that it is safe from the privy of hackers and cybersecurity criminals. How many of these have you already deployed? If you haven’t checked off every possible way to secure your email server, a good time to start is NOW.


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Are there any more methods to secure an email server? Do enlighten us through comments or direct message.