This page describes Thunderbird's configuration options that affect character encoding.

Specify the default character encoding for newsgroup messages

Menu location: ToolsEdit > Accounts Settings > <newsgroup account name> > Server Settings

Specify the default character encoding for messages in a folder (IMAP folders only)

Menu location: Edit > Folder Properties > General Information

Specify whether a folder's character encoding should override a message's character encoding (IMAP folders only)

Menu location:Edit > Folder Properties > General Information

Specify the default character encodings for sending and receiving messages

Menu location: Thunderbird > PreferencesTools > OptionsEdit > Preferences > Display > Formatting - Advanced button