From Mandriva Community Wiki

Thunderbird is the reincarnation of the Mozilla Mail component of the (now-defunct) Mozilla suite.

[edit] Text options and emoticons

Thunderbird has some very nice features which enable one to create e-mails in a kind of word-processed format.

These include changing colours, fonts, emboldening, underlining and italicising text and also putting graphical emoticons in your outgoing messages.

Unfortunately these features are fairly well hidden but can be accessed as follows:-

In the main tool bar, go to Edit->Preferences->Composition->Send options->Send the message in both plain text and html, and then a new tool bar opens under the Subject line in Thunderbird's compose screen. Clicking on the buttons on this toolbar engages the above features.

For your correspondents who prefer plain text e-mails, that option can be set in the address book against each particular entry. Also, it is good practice when sending messages to newsgroups or mailing lists, to send them in plain text. Many users are still on slow dial up services and do not appreciate html mailings, which the above features use. HTML mail is also a problem for users that receive the list in digest form.

And many experienced users just plain despise it.