Rated 4 out of 5 stars

Same comment than Nick: TBTracer doesn't succed to set the env. var. under Ubuntu (11.10). So I just cannot use it.

[edit] I find a workaround! From the command line, enter the 5 followwings lines one by one:

NSPR_LOG_FILE=/tmp/tbtracer.log
export NSPR_LOG_FILE
NSPR_LOG_MODULES=NNTP:1,SMTP:2,POP:1,IMAP:5,sync:1
export NSPR_LOG_MODULES
thunderbird

It should work now.
[/edit]

This review is for a previous version of the add-on (0.6).