More than a year ago I discovered a "tool" that I have to say has given me more insights about people than any other contact add-ons that are out there and has helped me when assessing the trustworthiness of a source. Called Rapportive, this is an extension for Gmail that lets you automatically visualize an email sender's complete profile..right inside your inbox.
This free add-on works for Firefox,Safari,Mailplane and Chrome, it is quick, efficient and doesn't seem to slow Gmail down in anyway (whew)
The only downside to Rapportive is that it only works for Gmail and where that is not an issue for me personally ( I only use Gmail), it might not be a good tool for you.
If you want to know more about Rapportive here is a video by Modeling The Masters ( Evan Carmicheal of Ecademy | a series of short videos, discussing how famous entrepreneurs got their start as well as some other worthwhile videos about growing your business) that does a pretty good job explaining how to use this extension.
Other advantages:
1. Rapportive replaces those annoying Gmail ads and replaces it with valuable information about the people who are sending you mail.
2. You can write notes and reminders about your different email contacts
3.For a person who is working on line having a CRM tool( customer relationship management), then helping with interaction with your customers or teams is going to be pretty darn useful!
If this is a tool that you want, here is the link to go through ->
rapportive