I can only see the message sender's name, not address!

By default, if the sender, CC or BCC's address is in your address book, Thunderbird will display the person's name but not their email address when you view a message.

To disable this behavior, select Tools > OptionsEdit > PreferencesThunderbird > Preferences. On the Advanced panel > Reading & Display tabDisplay panel > Advanced tab, uncheck "Show only display name for people in my address book".