[Exim] "@@" mechanism in a ${lookup } command

Hi!

I have a file like:

domain1        user1:user2:user3
domain2        user4:user5
...

This is the format user by the mechanism "@@dbm;/file/name"

I need to add a header (headers_add in a transport) if the $return_path
is listed in the file.

But how do I use that feature in a ${lookup } command?

When I use:

headers_add = "${lookup{$return_path}@@dbm{/my/list.dbm}{X-Header: yes}}"

Exim says "Failed to expand headers_add or headers_remove: missing
lookup type".

Am I forced to use a simple linear list for ${lookup }?

regards,

Marcin
--
Marcin Owsiany <marcin@???>              http://marcin.owsiany.pl/
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