[exim] system filter does not pick recipients from a header

Hello,

I've been trying to catch messages from a certain user to another user by a system filter
and deliver those to someone else.

My condition is:

if "$h_from:" contains sender@??? and
"$h_to:" matches name.surname@???
then
    deliver someonelse@???
    finish
endif

However the recipient field remains empty:
Match expanded arguments:
Subject =
Pattern = ^.*name\.surname@domain\.com
Sub-condition is false: $h_to: matches ^.*name\\.surname@domain2\\.com

I've checked the exim FAQ for filters and it mentions the variable $recipients could be
used here, because at filter time the recipient field might not be available, however I get:

Filter error: failed to expand "$recipients" in filter file: unknown variable name
"recipients"

The message gets delivered to the original recipient, so there's nothing wrong with it. If
you require the header please let me know and I will email it, as I'd prefer to avoid
posting it here.

--
Regards

Patryk