Gmail – How to Attach a File in the New Interface

Google in their infinite wisdom have made the feature an option through the Gmail Labs. This support page details the procedure to enable it:

1. Click the gear icon in the upper right, then select Settings.
2. Select the Labs tab.
3. Select the 'Enable' button next to 'Inserting images'.
4. Click Save.
5. When you're composing a message, you'll see an icon in the Gmail toolbar, between the "Insert emoticon" (smiley face) and "Link" buttons. Click that to insert an image.

You can add either a URL or a file you've saved to your computer - however only adding from your computer will attach the file to the email.

This is a known issue with all of Google's services. They do not support the .eml or the less common .mht, both of which are known and established formats. In this case it has been (for years now) one area that all the others (Microsoft, Apple, Mozilla, and most of the rest of the community) are ahead of Google on. The only option, aside from convincing Google to support it, appears to be to either bear with the extra info and read it as a raw text file or to save it and open it with almost any other email client, such as Thunderbird or Outlook.