We all know that emails that move across your server can contain highly sensitive data. Therefore, having your email server hacked has a lot of risks, each having a different impact:
- When spam lands in your subscribers’ inboxes it can cause a lot of complaints against your domains and IP addresses.
- Also, both Mailbox Providers (MVP’s) and subscribers could block your email.
- Spam could also lead to less subscriber engagement with your real emails.
- Finally, if unauthorized content is being shared from your email server, you risk being blacklisted.
This all can be easily prevented by securing your email server.
Here are some tips on how to secure your email server:
1. Configure mail relay to avoid being an Open Relay
It’s super important to configure your mail relay parameter and make it as restrictive as possible. By doing this you can restrict communication with unknown sources. Misconfiguration can be harmful because hackers and spammers can use your server as a gateway. Which could mean that your server will be blacklisted.
Users’ passwords are transmitted in clear text, which makes them easy to hack. Therefore, you should always make sure that you’re using secure connections. Use SSL and TLS and encrypt POP3 and IMAP authentication.
3. Maintain local IP blacklists
Make sure to maintain a local blacklist to block any domain or IP address that specifically targets you. By doing this you stop unwanted internet connections from bothering your messaging system. Also, make sure to check DNS-based blacklists (DNSBLs) and reject mails from IPs on that blacklist.
4. Access control with SMTP authentication
It’s important to protect your server from unauthorized access. To do this you can implement authentication and access control. SMTP is a great option to prevent abuse of your server and open relay. When it’s configured in the right way, only reliable accounts will be able to use your servers SMTP to send or receive emails.
5. Activate reverse DNS
By activating reverse DNS you can fight off unauthorized mail senders. Once it is activated, your SMTP verifies that the senders IP address matches both the domain names and the host that were submitted by the SMTP client. If it doesn’t match, messages can be blocked.
6. DKIM, DMARC and SPF
DMARC, also known as “Domain-based Message Authentication, Reporting, and Conformance”, is built around SPF and DKIM. With SPS you can define which IP addresses are allowed to send emails for a domain, while DKIM provides an encryption key that verifies that an email was not altered. DMARC requires that SPF or DKIM pass.
The security of your email server is a building block for establishing long-lasting relationships with your customers and is closely tied to your sender reputation.