Gmail to End Support for 3DES Encryption in Incoming SMTP Connections by May 30, 2025

Google is gradually phasing out support for the Triple Data Encryption Standard (3DES) in incoming SMTP connections to Gmail. Email systems that currently rely on 3DES to send messages to Gmail must upgrade to a more modern encryption method to ensure successful delivery, or else their messages will not be received.

The deadline for this transition is set for May 30, 2025.

3DES is an encryption algorithm that applies an older data encryption standard three times to each data segment, utilizing a relatively small block size of 64 bits. This limitation can lead to vulnerabilities, especially when a significant amount of data is encrypted using the same key over time. Additionally, it operates much slower than contemporary encryption standards like AES.

Google has stated that this update is essential “to enhance security and protect against potential vulnerabilities associated with outdated encryption methods.” The company urges email system administrators that send emails to Gmail to “ensure that all sending systems are configured to use more modern and secure TLS ciphers.”

Google Workspace domain administrators who have recently been utilizing 3DES to send emails to Gmail have also been informed via email. If their end users encounter issues, they may receive an alert indicating that the specific cipher is no longer supported.

Previously, data classification labels for Gmail were released in a public version. This feature enables organizations to categorize emails using custom labels or through classifiers already in use on Google Drive.