Another way you could attach an email by clicking on the 3 dots in an opened email. Under that “Forward as attachment” will be there. Click on it so it will get attached to a new mail.
There are situations where attaching emails makes more sense than forwarding separate emails, like wanting to forward multiple messages related to a single topic. With this new functionality, you can do exactly that. Sending emails as attachments allows you to write a summary email message to your recipients, and attach the set of supporting emails that recipients can directly open in their mail client.