Gmail's newest feature is definitely an interesting one, weird as it may sound. The email service will let you attach emails to other emails - without needing to download them first. Just drag and drop one or more emails into the Compose window and you're all set. Alternatively, you can select one or more emails from the conversation view, and using the overflow (three-dot) menu button select "Forward as attachment". This sounds a bit out there, but there apparently are situations where attaching emails makes more sense than forwarding separate emails - say if you want to forward...
Source: https://www.gsmarena.com/gmail_will_let_you_attach_emails_to_emails-news-40487.php
