In Gmail, an email attachment is indicated with a paperclip icon. If you receive a lot of email messages with various types of files as attachments, you’ll have to open each message to know what kind of file is attached. To makes things easy, have a look at the Chrome extension Attachment Icons for Gmail.
Once installed, the extension identifies email attachment file type and replaces the generic paperclip icon with standard Windows icons for JPEGs, PDFs, MP3s, ZIPs, spreadsheets, and many other file types. This enables you to know what kind of attachment an email has straight from your inbox without opening the mail.
Attachment icon is added right next to the date in each email (not next to the star icon as seen in the Chrome Web Store image), as well as the mail headers. In case an email consists of multiple attachments, then the icon of the last attached file is used.
If you are a Firefox user, you can get this functionality by installing the Better Gmail 2 add-on. It can show custom icons (from script) or file icons that are native to your operating system.
Along with attachment icons, the add-on adds several other optional features such as row highlights, hide chat, hide invite box etc., that are all based on individual user styles. If you don’t want the extras, get only the attachment user styles from these links: Gmail with different attachment icons, Gmail 2 – native OS attachment icons. Do note that you have to install either Stylish or Greasemonkey add-on before you can use any of the user styles.
That’s it! You no longer have to open and scroll down lengthy emails just to find out what type of attachment an email has.