Mail PassView is a tiny portable tool for recovering user names, passwords and other details for many popular email accounts and services.
The program supports Outlook 2000-2013, Gmail/ Hotmail/ MSN mail/ Yahoo! Mail (if the password is saved locally), Thunderbird (if the password isn't encrypted by a master password), Windows Mail/ Live Mail/ Outlook Express, IncrediMail, Eudora and more.
To use the program, just download and run it. Any details detected are displayed in a table containing the following fields: Account Name, Application, Email address, Email server, Server Type (POP3/IMAP/SMTP), User Name, and Password.
As usual with NirSoft tools, any recovered data can be saved in a text report for easy reference later.
There's also a simple command-line interface. Running mailpv.exe /stext c:\passwords.txt in a script, for example, saves all your passwords in the specified file without displaying an interface.
Please note: security software will sometimes highlight Mail PassView as a threat. This is because it could be used maliciously, for example by someone else to steal the passwords from your machine: the program isn't otherwise dangerous in any way.