While confidential mode could help prevent information leaks, Google notes a few caveats. It won't, for example, prevent recipients from taking screenshots or a snap of the message.
Also, confidentiality could be compromised if the recipient is using a malware-infected computer.
Google is treading more carefully with the rollout of confidential mode for its G Suite users, despite calling confidential mode an "information rights management" control.
The feature is currently off by default in G Suite and users need to ask their admin for permission to access it.
Some people contest Google's use of the word 'confidential', arguing it might mislead people into expecting true confidentiality when in fact it doesn't.
The Electronic Frontier Foundation recently (EFF) accused Google of providing "misleading assurances of privacy and security" with the feature, which could steer users away from finding more secure ways to send private messages.
Its main criticism is that Gmail isn't an end-to-end encrypted service, so Google could read your email.
In response to recent concerns about third-party developers having access to Gmail users' content, Google stressed that no one at Google reads Gmail messages but noted that it can if it needs to, to investigate a bug or abuse.
EFF's other criticism is that expiring emails are only partially erased since they remain in the sender's sent folder after the expiry date and need to be manually deleted from that folder.