My own Greek draft transforms into gibberish, unable to read it.
The main text of the draft, in English, re-appears properly. The change affects polytonic & normal Greek, and Hebrew parts of the message. Both directly printed passages and copy-pasted from MS Word are scrambled.
Wot ksenaki
Wšě wotmołwy (1)
Any email that contains information pasted from word has a suspect structure.
SO when you compose these mails in the Thunderbird composer does this occur?
When does the conversion occur? Are you using the BiDi add-on for your Hebrew? Is the character set Unicode? When you right click your drafts folder and select properties is the character encoding set to UTF-8 or Unicode