AN email client is by definition an interface. It interfaces with the Email server, and gives you a GUI to view, instead of CLI.
But, anyways.....email has the domain name imbedded......you know the stuff that comes after the @ symbol. Thats all you can get from an email as far as indentifying information. And the kicker is, that a person could, just bounce an email around enough times, that the original sender information is essentially LOST. its what folks use to to stay anonymous when sending emails.
As far as the actual Email account information (persons name, address, phone number, SSN, etc etc), in a public database, im afraid you are out of luck.
Most notably because FREE email accounts dont require verifying a persons identity, and that it matches up to a real person.
So, what exactly, within SquirellMail (SM), might i be able to help you with?
See, the SM wants your email and password ***** for the domain name Email server. (The IANMACAULAY.com domain)
Or is there something else i am missing?