[Exim] use of gecos field

I am baffled by Exim's use of gecos_pattern & gecos_name on several counts:

First, I want Exim to completely ignore the gecos field, but don't see how to. I
tried setting gecos_pattern to something which would never match:

- gecos_pattern = "^(,,)$"
- gecos_name = $1

but Exim then used the whole gecos field, presumably because gecos_name is then
unset. How do I get it to leave my From: and Sender: headers alone?

Second, I have a configuration which does not regard any user as local and forwards
everything to another system. Even this uses the gecos field to modify the From:
header! The config file is:

-  #                    MAIN CONFIGURATION SETTINGS
-  primary_hostname = local.at.here
-  qualify_domain = domain.at.here
-  local_domains =
-  forbid_domain_literals
-  never_users = root
-  locally_caseless = false
-  end
-  #                      TRANSPORTS CONFIGURATION
-  remote_smtp:
-    driver = smtp
-  end
-  #                      DIRECTORS CONFIGURATION
-  end
-  #                      ROUTERS CONFIGURATION
-  smarthost:
-    driver = domainlist
-    transport = remote_smtp
-    route_list = "* smarthost.at.here bydns_a"

How can this go looking at the gecos field when nothing is local?

My main need it to just ignore gecos, so help with that will be mose welcome.

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Phil Chambers (postmaster@???)
University of Exeter