[Exim] rewriting question

Dear exim-users,

I have an exim (2.12) hub acting as smarthost for a Novell Groupwise
mail server. The Groupwise machine occasionally outputs broken header
lines in messages, e.g.:

To: inet:joe@???, inet:fred@???

The envelope receipients are correctly set so the message is delivered
to joe@??? and fred@???. But, if joe@??? does
a reply-to-all, he ends up mailing "inet:fred@???" which
fails.

I tried to remove the "inet:" with a rewriting rule like this:

^inet:(.*)$             $1                              S

thinking to do the rewrite before the address is validated. This is
close, but not quite there:

# exim -brw inet:dave.holland@???
1999-11-10 16:01:16 "inet:dave.holland@???" rewritten as "dave.holland@???" by rule 5
    SMTP: dave.holland@???
Syntax error in address: missing or malformed local part (expected word or "<")

What am I missing? Is what I'm trying to do possible?

Thanks for your help,
Dave
-- 
       Dave Holland        |       "To improve its usability, PowerPoint
      Systems Manager      |         slightly misdefines the size of a
       Incyte Europe       |             centimeter"  -- Microsoft
       Cambridge, UK       |