Really simple tool, but very effective!
Infoga is a python script that allows gathering email information with Google, Bing, and Shodan:
Infoga is a tool for gathering e-mail accounts information from different public sources (search engines, pgp key servers). Is a really simple tool, but very effective for the early stages of a penetration test or just to know the visibility of your company in the Internet.
The installation is really simple, just install some requirements (requests, urllib3, urlparse) with PIP and start the infoga.py script.