13 Tips on How to Secure Your Mail Server

It should go without saying that the security of your mailing infrastructure is inextricably linked to your sender’s reputation and serves as a foundation for developing long-term customer relationships.

Following are some of the consequences of a hack or spam in our inboxes:

  • Many complaints are filed against our domains and IP addresses due to this.
  • Subscriber engagement with our authentic email has decreased.
  • Our mail could be blocked by both subscribers and Mailbox Providers (MBPs).
  • Spam will very certainly be sent to random email addresses, which will almost certainly include a large number of spam traps.
  • We’ll almost certainly end up on publicly accessible blacklists.

1.Set maximum message Size

There’s a chance the server will crash if it processes huge mail messages, especially if we send them to numerous recipients simultaneously.

To avoid this, we define a maximum message size for your server that is acceptable.

2.IP Blacklists to Block Spammers

The implementation of a local IP blacklist on the email server is another reliable approach to stop spammers who exclusively target us.

3.Block Fake Senders via Reverse DNS

Spamming always begins with a bogus email address. As a result, setting RDNS for our server reduces it significantly.

Our SMTP ensures that the sender’s IP address matches both the host and domain names given by the SMTP client in the EHLO/HELO command once Reverse DNS Lookup is enabled.

4.Encrypt POP3 and IMAP Authentication for Privacy Concerns

Connections like POP3 and IMAP were not designed with security in mind. As a result, we will be able to use them without rigorous authentication. It is a significant flaw.

SSL/TLS is the most widely used and simplest method of implementing robust authentication. Encrypt POP3 and IMAP authentication and utilize SSL and TLS for safeguarding the mail server.

5.Activate SPF to Prevent Spoofed Sources

Domain owners can define who is allowed to send emails in their name using the Sender Policy Framework (SPF). It’s to keep faked sender addresses at bay.

When SPF is enabled, the MX record of the transmitting server is validated before messages are sent. If the email source is compared to the sender’s SPF policy, it can be determined if the email is forged.

6.To Control user Access, set up SMTP Authentication

We can use authentication and access control to safeguard the server against unauthorized access. SMTP authentication, for example, requires users who use our server to first get permission to send mail by providing a username and password.

Note: that this only applies if the mail server’s IP address is routed.

7.Carefully Configure Mail relay options to Prevent becoming an Open Relay

This feature is available on all mail servers. We can use it to tell our mail server which domains or IP addresses it should relay mail to. To put it another way, this tells our SMTP protocol who to forward mail to.

Misconfiguration of the same, on the other hand, can be harmful because spammers can use our mail server as a gateway to spam others, resulting in our IP address being blacklisted.

8.Limit Connections to Protect our Server Against DoS Attacks

We frequently have a large number of connections to a server at the same time. We update the configuration file to set the connection limit for a server. By doing so, we can greatly reduce the risk of DoS assaults on our server.

Check factors like the total number of connections, the total number of simultaneous connections, and the maximum connection rate to handle connection limits.

9.Enable SURBL to Verify Message Content

SURBL (Spam URI Real-time Blocklists) evaluate emails on the basis of invalid or malicious links within a message.

This filter guards users from malware and phishing scams. SURBL will not be supported by all mail servers. If our email server supports it, though, turn it on.

10.Have at least 2 MX records for Failover

For availability, a failover setup is critical. Setting up at least two MX records for each domain is strongly recommended by our Support Techs.

The main is used first, and the secondary is used in the event that the primary fails for whatever reason. This is possible at the DNS Zone level.

11.Implement DKIM (DomainKeys Identified Mail)

DKIM (DomainKeys Identified Mail) is a TXT type record and an email authentication technique.

This approach is based on encryption and a fingerprint hash, which validates the email and identifies the sender to the receiving mail server.

12.Implement DMARC

To offer even more security, DMARC (Domain-based Message Authentication Reporting & Conformance) employs the SPF and DKIM protocols, which provide reporting from receivers to senders.

This allows us to keep track of our domain and increase the security of our mail server.

13.Use DNSBL to Block Malicious Emails and Domains

Spam blocking lists are known as DNSBLs (Domain Name System Blacklists). It enables us to keep our server free of spam and malicious software.

The more DNSBL connections you have, the better.

Maintaining your mail server’s security is essential for a successful email program and getting the most out of the Certification program. Improved email deliverability at major MBPs, circumventing crucial MBP filters, unblocked photos, and active links are just a few advantages. Suppose the Compliance team detects spam on your Certified IP address/domain. In that case, your IP address/domain will be suspended from the Certification Program, and performance metrics may take 30 days or more to meet Certification standards.