STARTTLS and SSL/TLS? Email Encryption explained

August 2, 2022  |  2 min read

STARTTLS and SSL/TLS are standard protocols used to secure email transmissions. We are sometimes confused by the differences between these abbreviations. 

In this article, we will get to discuss the role of SSL/TLS and STARTTLS in email encryption and get to understand what each means. 

What’s the role of STARTTLS? 

STARTTLS is mainly used when an email client (such as Gmail, Outlook, etc.) wants to upgrade an existing insecure connection to a secure connection using SSL or TLS, it is used to inform the email server of this. 

STARTTLS is also used with the IMAP protocol, which is typically used to get emails from an email server, in addition to SMTP. POP3, another email-receiving protocol, makes use of a similar command known as STLS

The Need for STARTTLS and SSL/TLS  

It’s crucial to employ email security protocols like STARTTLS and SSL/TLS since insecure email is a common attack vector for cybercriminals. Without taking this precaution, users are vulnerable to email spoofing which could lead to password theft and financial losses 

However, cybercriminals aren’t as fortunate if an email is intercepted with STARTTLS or SSL/TLS in place. These emails cannot be decrypted without the decryption keys, which are only available to the email server and client. 

How do TLS/SSL and STARTTLS work? 

A client connects to a server to inquire about the validity of an email before it is sent. It explains the SSL/TLS versions it supports as well as the type of encryption it uses. To prove its legitimacy, the server replies with its digital certificate. Once everything is in order, the two parties create and share a special key that will be used to decrypt messages in the future. 

Read about which ports are used in SSL/TLS. 


Skysnag’s automated software safeguards your domain’s reputation and keeps your business away from compromised business emails, password theft, and potentially significant financial losses. Our automated DMARC reports save you time from reading lengthy, perplexing reports while encrypting sensitive information in your emails.  Get started with Skysnag today by signing up for a free trial.