Emails form a central part of business communications, enabling teams to collaborate, share documents, and follow up on each other. The ease of sending and receiving messages has many benefits. However, it can also make your business vulnerable to hackers – 96% of organizations have been targeted by an email-related phishing attempt. With this in mind, staying on top of your security has never been more critical.

Your business email servers are responsible for every department and employee’s incoming, and outgoing emails. By ensuring these are secure, you can reduce the number of spam emails finding their way into your system, and identify them efficiently to prevent them from causing future issues. This means your employees can trust their emails as a channel to communicate, not spending time dealing with the risks of hackers or phishing emails.


Why Is Email Server Security Important?

Emails are used company-wide to prevent communication silos, schedule meetings, and share files. For businesses of any size, being hacked is a real and present danger that can delay processes, damage your internal systems, and undermine your business values. Although taking security measures doesn’t eliminate all chances of hacked emails, it significantly reduces the quantity of phishing reaching inboxes, and prevents data from being lost.

Email servers are the first opportunity to stop incoming spam emails before reaching the individual inboxes of employees. Likewise, it’s also the last chance to implement security features on outbound emails to prevent them from being hacked. As hackers become more advanced in their methods of hijacking emails, extra safety measures are needed to identify tampering with email content, and find fraudulent addresses that indicate unsafe emails.


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How to Secure Your Email Server


  • End-to-end Encryption

This feature is becoming more and more common across communication channels, including your VoIP system, and online video call software. End-to-end encryption means that from the moment an email is sent until it is opened, the content of your email is encrypted so that interceptors are unable to read it. Multipurpose internet mail extensions (MIME) apply this to all emails, preventing your private conversations from being accessed by external hackers. 

Both S/MIME and PGP/MIME services use certificate-based encryption, verifying the sender information. This means that when your email arrives with your recipient, their server can authenticate your address as the sender, proving its validity. These security features may not be available in all inboxes; however, there will be other encryption settings, add-ons, and software integrations to provide these options. 


  • Enable SPF

Sender policy framework (SPF) is used to ensure that the sender address is the actual sender. This checks the IP address of the sender, the server the email has been sent from, and the domain against those that are trustworthy to provide authentication. For example, if you register ae domain names for your email, your IP address should match this. If the IP doesn’t match, the sender probably isn’t a trusted source, and SPF blocks the incoming email.

SPF features can be found within your email server’s authentication settings or can be set up using external software integrations for your inboxes. Once set up, any email that fails the sender authentication will be bounced, meaning it won’t reach your employee inboxes, and it will return an error message to the sender. Using SPF ensures all the emails your business receives are from the sender they claim to be from.


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  • Credential Authentication

Using fake credentials is an easy way for hackers to gain the trust of email recipients, acting as someone familiar to attack your software, and business. Open relay servers are unable to identify this, as they allow emails from anyone to be received. Nonetheless, other settings are available to ensure the credentials of emails you receive are legitimate alongside protecting the credentials of outgoing emails from your business server, even on automated emailing.

Credential authentication highlights sender IDs that don’t match where the email is sent from, and fake email addresses. You can also encrypt your email credentials or use transport layer security (TLS). This ensures your email is secure when in transit, preventing the sender’s credentials from being manipulated. It also means emails from your servers are protected from being cybersecurity threats, keeping both your messages, and recipients safe.


  • Set Up a DNSBL

On the whole, you can recognize the servers, and addresses where your incoming emails are coming from. With this thinking, you can create a domain name systems blacklist (DNSBL) marking specific domains, and addresses to block emails from. This is also useful with repeated spam from the same sources or IP addresses, preventing these emails, and even the VoIP call from reaching your company. 

A DNSBL isn’t a literal list of email addresses but rather a software that recognizes the patterns, and uses criteria to determine spam addresses. This connects to DNSBL servers globally, checking the sources of incoming emails. The measures in place highlight domains or IP addresses worldwide that are untrustworthy or have previously sent spam, blocking their emails. As new spam email addresses, and servers are discovered, the criteria eliminates them too.


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  • Use SMTP Services

A simple mail transfer protocol (SMTP) can be used for sending emails from your server. Using SMTP services ensures this protocol is protected, and secure. The more SMTP connections your server has, the more vulnerable it is, as there is a higher chance of hackers gaining access. Adding safety features to your SMTP limits the issues seen with open relay servers, preventing server misuse by reducing connections, and accessibility.

Whether by setting up passwords and usernames to access the server or encryption services, these avoid breaches of data, and malware attacks. This reduces the number of known accounts able to access the server, and protects those connections from hackers. Your server settings are then less vulnerable and exposed, ensuring your business emails, and data remain secure and in line with ISO compliance through the use of SMTP services.


  • Content Filtering

Most spam folders work by using some form of content filtering to highlight suspicious content, and remove it from your inbox. These filters scan your incoming and outgoing emails’ content, titles, and sender information, including the metadata, to find matches that class the email as spam. Generally, content filters act as a last resort after other email security features have scanned emails, matching email content to the criteria for spam. 

Email filtering services can be adapted to suit your business, and ensure the right emails are being blocked from your inbox. This can identify specific phrases, addresses, or links that are likely to be spam. However, this only reduces the harmful emails in your inbox, and can be wrong occasionally. It requires individuals to review their spam folder regularly for miscategorized emails, and approach their inbox with awareness.


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Email Security Best Practices

Protecting your business email server also comes down to the actions of your employees. Suppose they use their work emails securely as part of their asynchronous communication, and make wise decisions regarding email safety, even if spam emails get through. In that case, they will cause less damage. Reminding your employees regularly of email security best practices can help protect the whole business. This includes things such as:

  • Use double authentication – password protecting and using access codes to log into work emails makes it harder for hackers to gain access to internal email addresses, and information
  • Be cautious of links – especially links to unknown webpages can be malicious. Check links are directing you to where you expect, and if unsure, avoid clicking on them
  • Don’t share private information – although your server protects your outgoing emails, the only way to be sure hackers can’t use your data is not to share it
  • Respond only to known email addresses – when receiving mail from unknown addresses, always treat it with caution, and avoid responding until you are sure of its source
  • Use secure internet connections unsecured and public wifi connections can be more accessible for hackers to break into your emails, so avoid using them


How Can You Enhance Your Email Server Security?

Communications are central to your company, from your cloud based business phone system to your emails. Many of these suggestions work together, even across different communication channels, to increase security. The more measures you have in place, the harder it is for hackers or spam emails to make it through to your employee inboxes. This reduces the opportunity for viruses, malicious content, and data breaches to occur.



Begin implementing these safety measures, and starting the conversation around email security in your business. Once in place, each safety feature automatically filters your emails, so your server stops incoming spam emails, and protects your outgoing emails. Setting them up for your server protects every employee’s inbox from one location. Putting the effort in now stops future attacks, minimizing the potential damage of phishing, and email hackers.



Richard Conn – Senior Director, Demand Generation, 8×8


Richard Conn is the Senior Director for Demand Generation at 8×8, a leading communication platform with integrated contact center, voice, video, IP phone, and chat functionality. Richard is an analytical & results-driven digital marketing leader with a track record of achieving major ROI improvements in fast-paced, competitive B2B environments. Here is his LinkedIn.

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