After that last four-week stretch, users will be pushed to the new Gmail permanently with no option to opt-out.
As Google explains, anyone can opt in to the new design at the moment.
"To prepare you and your organization for the general availability (GA) launch, the new Gmail is on an EAP and customers can choose to participate (or not) at the domain and organisational unit levels", Google said in a blog post.
In April, Google unveiled a new design for Gmail, which features a more modern look, advanced security features, artificial intelligence, and more integrations with other G Suite apps. Those who get it can opt-in to use it if they want or they can't if their G Suite account administrator hasn't enabled it.
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The confidential mode will allow users to set an expiration date for sensitive emails on their Gmail, sending recipients a link to content rather than the full email to make sure it can be safely deleted.
From there, gradually all G Suite users will be transitioned to the new Gmail across two phases.
Admins can also give users the option to try the new Gmail at their own pace or - and this is the default setting - they can just wait another four weeks and then Google will automatically give users the option to opt in. And, then onwards, users can no longer opt out of the new mail.
Though some Gmail users have criticized the design, most reviews online appear to be neutral or positive. According to Gmail, more details surrounding the transition will be announced.
Also, It's now the only version of Gmail that supports a feature called Smart Compose, which finishes sentences with the aid of machine learning and artificial intelligence.