New Thunderbird checklist

Check all IMAP folders:
By default Thunderbird only checks the inbox for new messages, but since we use server side filter emails don’t have to go to inbox and sometimes go directly to destionation folder.
Fortunaltely Tunderbird can be configured to check all folders, but it has to be done manually, put the follwoing lines in “user.js”:

// Download mail from all accounts on startup
user_pref("mail.check_all_imap_folders_for_new", true);

The file doesn’t exists by default so you need to create it in your “profile” filder, this link will help you to locate your “profile” folder:
http://www.mozilla.org/support/thunderbird/edit#profile

Disable return receipts:
I don’t why people use this feature it is bit annoying, so I usually disable requesting and replying to “return receipt”:
Edit -> Options -> Composition -> General -> Return Receipt
Uncheck “When sending message, always request a return receipt”
and select “Never send return receipt”

Customize Encoding
Open new Compose windows (CTRL+M)
Options->Character Encoding->Customize list
I always delete everything and keep “Arabic (Windows-1256)” , and “UTF-8”

Then to change the default character encoding:
Tools->Options->Dispaly->Fonts
Select “Arabic (Windows-1256)” as default for incoming and outgoing emails.
Check “Apply the default character encoding to all incoming messages.”
Check “Use the default chacter encoding in replies”

Update:
Install BiDu plugin BiDi plugin, to support right to left editing.