Gmail to drop support for 'outdated' 3DES encryption in incoming SMTP connections

Google is phasing out support for the Triple Data Encryption Standard (3DES) in Gmail's incoming SMTP connections. In plain terms, email systems that still use 3DES to send messages to Gmail will need to switch to a more modern encryption method. After the cutoff, if a server tries to connect using only 3DES, the message won't make it through.

The deadline is May 30, 2025. From that point on, email traffic relying on 3DES will not be delivered.

3DES is an encryption algorithm that applies the older Data Encryption Standard three times to each chunk of data. While this offered better protection than single DES, which became easy to break with faster computers, 3DES itself is now considered outdated. It uses a relatively small 64-bit block size. This limitation makes it vulnerable when a large amount of data is encrypted using the same key over time, potentially allowing attackers to figure things out about the content. It is also much slower than modern encryption standards like AES. For these reasons, 3DES has been on its way out for years, disappearing from many web browsers and other secure connections.

Google stated the change is needed "to improve our security and protect you from potential vulnerabilities associated with outdated encryption methods." The company is telling administrators of mail systems that send to Gmail to "ensure that all of your sending systems are configured to use more modern and secure TLS ciphers."

Admins for Google Workspace domains that have recently used 3DES to send email to Gmail were also notified by email with more specific information. If their end users are running into issues related to this, they might see a warning indicating the specific cipher is no longer supported. This removal affects all Google Workspace customers and anyone whose mail server sends email to any Gmail user.

In other Gmail news, the service recently made its data classification labels generally available. These labels let organizations categorize emails for better data protection and management. Gmail also added the ability to react to emails quickly using emojis on web and mobile interfaces. Furthermore, Gmail's search function is getting an upgrade with AI to prioritize the "most relevant" results based on factors like recency and how often you interact with emails or contacts.

Source

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