Gmail Sender Icons is a Google Chrome extension that makes it easy for you to quickly and visually identify email senders in Gmail. It shows the company domain name of the email sender and the official logo (favicon) of the sender's organization alongside the email message.
To give you an example, if you receive an email from email@example.com, the Gmail extension will add a virtual label google.com to your email message and also a logo of the Google website next to the message so you can immediately identify the sender in the email list.
Gmail Sender Icons has been featured on Product Hunt, LifeHacker, The Next Web and host of popular websites.
The favicons and the sender's domain are visible across Gmail including search results. The sender's label is applied virtually and the actual labels of the email message are left unchanged.
The Gmail Chrome extension uses the Google S2 service for generating the website's favicon while the Gmail messages are parsed with the Inbox SDK framework. All processing is done locally in your browser and no Gmail data is ever shared or uploaded anywhere.
The add-on is open source and the code is available on Github.