Ah, one thing that just occurred to me is that you can't use the E,F,T or S rewrite flags on a headers_rewrite option. So, you may have to have a redirect router that detects your local part format and then redirects the mail to the gmail address. After some messing around how about:
1) You go back to your rewrite
2) You use an acl variable in the rcpt acl to note when the localpart matches what you want
3) You have an unseen redirect router that notes the acl variable is set.
So:
Stick the rewrite rule back in as before.
In the ACL where you are doing rcpt checking add at an appropriate place something like:
warn local_parts = ^[.]\+onbehalf\$
set acl_c1 = foo
So you have an acl variable set then use that in a redirect router:
Special:
Driver = redirect
condition = ${if !eq{acl_c1}{foo}}
data = <whatever>
unseen
Does that sound reasonable to people ?
