Customer Support

In Thunderbird, the display name will be shown by default if the sender ID has set its display name.

There’s no provision to show both the email address and the display name in the email listing pane.

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,

1] Select Tools
2] Preferences
3] Go to Reading and Display
 4] Uncheck "Show only display name for people in my address book".

After disabling "Show only display name for people in my address book" it will show the email address of the sender.