Description of problem:
Today, I finally gave up on Thunderbird after using it for nearly a
year.  The reason why?  I'm a developer and I could not get thunderbird
to cooperate regarding my sent text.  I checked the boxes I could to turn
off word wrap.  I turned off html email.  Yet when I send an email
with an inline patch that contains tabs and spaces, Thunderbird
messes them up.  So people receiving my email tell me my patch does
not apply properly.

I've tried manually editing my config prefs.js and changing things
based on several people's recommendations.  Things like:

pref("mailnews.send_plaintext_flowed", false); // RFC 2646=======
pref("mailnews.display.disable_format_flowed_support", true);

Nothing fixes it.  IMHO, every email client should have the option
to turn off all formatting, such as word-wrap or changing tabs into
spaces, or deleting spaces, etc., and it should be a simple
user-friendly button.  Editing the prefs file is not user-friendly,
even if it did work.  I always format my own text, so I never want
my email clients to word wrap or change my content.

Version-Release number of selected component (if applicable):
thunderbird-1.5.0.12-1.fc6

How reproducible:
Always (for me at least)

Steps to Reproduce:
1. Compose an email.
2. Generate a simple code patch using diff -pu > /tmp/gronk
3. Edit /tmp/gronk with xemacs or some such.
4. Select the entire patch text.
5. Paste it all into your email.
6. Send it to yourself.
7. Receive it with some other email program, like mutt or evolution.
8. Use something like diff to compare it to the original, or better 
   yet, try to apply the patch.

Actual results:
For example, unchanged lines of source will be missing the starting
space " ".  Added lines will be okay and have "+" as expected.
The email might look okay to thunderbird, but it won't be okay.
I've even have patches that look bad in thunderbird, but it somehow
magically fixes them when you save them with thunderbird.

For example:
diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index c7c6ec0..170ba93 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -354,7 +354,9 @@ struct gfs2_trans {
 
	unsigned int tr_num_buf;
 	unsigned int tr_num_buf_new;
+	unsigned int tr_num_databuf_new;
	unsigned int tr_num_buf_rm;
+	unsigned int tr_num_databuf_rm;
	struct list_head tr_list_buf;

Expected results:
The patch should diff against the original.  The content should not
be modified.  There should be a " " or "-" or "+" at the start of
every line.

For example:
diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index c7c6ec0..170ba93 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -354,7 +354,9 @@ struct gfs2_trans {
 
 	unsigned int tr_num_buf;
 	unsigned int tr_num_buf_new;
+	unsigned int tr_num_databuf_new;
 	unsigned int tr_num_buf_rm;
+	unsigned int tr_num_databuf_rm;
 	struct list_head tr_list_buf;

Additional info:
Patch lines typically have tabs following the leading space.
I've had some people say "works for me" but they were at older
versions of thunderbird.  I just did a yum update, so it's the
latest for FC6 AFAIK.