[exim] User's forward file is not always obeyed

Hi.

I have been using exim for a very long time now. A year or so ago I
upgraded from exim 3 to exim 4. I use spamassassin to add headers to the
incoming emails, using the built-in exiscan system and a spamd server. I
then use a .forward file to define what happens to my mail. Here is part
of my forward file:

if $message_headers contains "X-Spam_bar: +++++++++++" then
         save $home/mail/mail/spam
         finish
endif

if $message_headers contains "X-Spam_bar: +++++" then
         save $home/mail/mail/guessedspam
         finish
endif

Over the last few weeks, a few spam messages have started to be delivered
to my inbox, even though they are marked as spam by spamassassin. These
messages definitely have a header saying "X-Spam_bar: +++++++++++++" or
longer, yet the rule in the .forward file redirecting the mail to my spam
folder is not being obeyed. Only a few of the messages are affected. The
majority of my incoming spam is still redirected to my spam folder.

Has anyone else had this problem? Is there a possibility of a race
condition introduced in exim over the last couple of months? Does the
exiscan always run before the .forward file is processed?

Any help would be appreciated.

Matthew

-- 
And why do I do it that way? Because I wish to remain sane. Um, actually,
maybe I should just say I don't want to be any worse than I already am.
         - Computer Science Lecturer