Gmail drops support for 'outdated' 3DES encryption

Google is phasing out support for the 3DES (Triple Data Encryption Standard) encryption standard for incoming Gmail SMTP connections. Simply put, any email system that still uses 3DES to send messages to Gmail will have to switch to a more modern encryption method. After the deadline (May 30, 2025), if a server tries to send an email using only 3DES, the message will not be delivered.

Why was 3DES removed?

3DES is an encryption algorithm that applies the old DES standard three times to each block of data. While it was once more secure than single DES (which was easy to crack), 3DES is now obsolete because:

1. Small block size (64-bit), vulnerable to attacks when encrypting large amounts of data with the same key.
2. Much slower than modern standards like AES.

For these reasons, 3DES has been slowly disappearing from browsers and other secure connections. Google said the change was intended to 'improve security and protect users from vulnerabilities in older encryption methods.' The company recommends that email system administrators sending to Gmail 'ensure all servers use modern, more secure TLS ciphers.'

Google Workspace admins who have recently used 3DES to send emails to Gmail will receive a specific email notification. If users are having issues with it, they may see a "this cipher is no longer supported" warning. The deprecation of 3DES affects all Google Workspace customers and email servers that send emails to Gmail users.

In addition, Google has also applied some other important changes to Gmail:

1. Data classification labels: Allows organizations to classify emails for better data management and protection.
2. Emoji Reactions: Add quick emoji responses on web and mobile.
3. AI-enhanced search: Improves "most relevant" search results based on factors like freshness, frequency of email/contact interactions.

Removing 3DES is Google's next step in pushing security standards, forcing organizations to update their systems to ensure email to Gmail is not interrupted.

David Pac

Update 26 May 2025