SMTPS: Port to use to secure SMTP with SSL/TLS

What Is SMTP?

SMTP is an acronym for Simple Mail Transfer Protocol. It is a set of communication protocols that allows applications to send electronic mail over the internet. It’s an application that uses email addresses to deliver messages to other computer users. It allows users on the same or separate computers to exchange mail.

It can transmit a single message to one or many recipients. Text, audio, video, and images may all be used to send messages. It can also send messages on networks outside the internet. SMTP is mostly used to establish communication rules between servers. The servers have a mechanism for identifying themselves and stating the type of communication they are attempting. They also have a system in place to deal with issues like wrong email addresses.



In comparison to SMTP, SMTPS adds extra SSL or TLS cryptographic methods for increased security. The ‘S’ stands for Secure.


The SMTP protocol does not include encryption by default, therefore it may be used to send emails without any security. As a result, emails sent using SMTP are vulnerable to man-in-the-middle attacks or bad actors eavesdropping while the email is in transit. SMTPS, on the other hand, uses asymmetric cryptography to encrypt email conversations using TLS or SSL.


Drawbacks of SMTP 

SMTPS-unsecured email is subject to a number of attacks that can alter the contents of a message or redirect it to an attacker before being delivered to the intended recipient.

By inserting their own malicious SMTP commands into data as it is transferred from a server, attackers take advantage of the unencrypted interactions. These attacks can be used to send spam from the vulnerable domain, steal sensitive data invisibly, or carry out phishing assaults.


Steps to Enable SMTPS 

Enabling TLS on your mail server will secure SMTP. Enabling TLS encrypts the SMTP protocol on the transport layer by enclosing it behind a TLS connection. This successfully secures SMTP and converts it to SMTPS.


SMTPS traffic is commonly routed on ports 587 and 465. STARTTLS, which allows the email client to establish secure connections by requesting that the mail server upgrade the connection to TLS, is frequently used to encrypt SMTP communications via Port 587. 


Implicit TLS is utilized on port 465, which can be used to allow secure email communications. This is suggested overusing STARTTLS on port 587, according to the IETF.

Finally, port 2525 is occasionally utilized. To prevent consumers from creating their own mail servers, some residential ISPs would restrict port 25. Hobbyists and tiny home enterprises utilize port 2525 to combat this.

Users can check their client settings to see if SMTP is enabled in their email client. Users of Outlook can confirm this by doing the following steps:


  • Click on ‘File > Accounting Settings’. Then open the Account Settings box.
  • Choose your email from the Email tab, then click on the ‘Change’ icon. In the Server Information section, ensure that the Outgoing Mail Server is set to your mail server address.
  • Under the Outgoing Mail tab, ensure that ‘SMTP requires authentication’ is checked.


SMTPS can be enabled by system administrators via their SMTP connector’s settings. Depending on whatever mail server you’re using, this step will be different. There are choices for specifying the authentication type when configuring the SMTP connection, and TLS is one of them.


SMTPS protects messages while in transit from prying eyes. What about spoofing, phishing, and spam, though? Let’s have a look at some email security standards you may use to secure your email and domain.


  • Sender Policy Framework (SPF): Assists receivers in verifying that messages sent from your domain are indeed from you. SPF informs the rest of the world about the servers from which you and other domain owners like you send emails. The SPF check fails if a message is received from your domain that does not come from these servers.


  • DKIM (Domain Keys Identified Mail) adds an extra layer of email authentication by adding a digital signature to the messages. This helps prevent tampering with communications while they are en route


  • DMARC (Domain-based Message Authentication, Reporting, and Conformance) is a technical definition for authenticating communications by combining SPF and DKIM capabilities. One of the greatest methods to defend your brand against impersonation is to have DMARC completely enabled on your domain.


  • Brand Indicators for Message Identification (BIMI) provides an extra degree of safety for domains that already use DMARC for authentication by displaying their brand logo in email communications. This makes it easier for receivers to tell if an email is real, and it also helps organizations increase brand recognition through email advertising.


EmailAuth helps you with all of the following by automating DMARC, SPF, DKIM, and BIMI for your brand and helps you secure your emails without additional hassle. Check out EmailAuth.

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