Recent example courtesy of T106462:

Received: from tools-webgrid-lighttpd-1201.tools.eqiad.wmflabs ([10.68.18.45] ident=Debian-exim)
	by mail.tools.wmflabs.org with esmtp (Exim 4.76)
	(envelope-from <root@tools.wmflabs.org>)
	id 1ZFJDM-0007Nr-Lt
	for tools.anagrimes@tools-bastion-01.eqiad.wmflabs; Wed, 15 Jul 2015 09:42:56 +0000
Received: from root by tools-webgrid-lighttpd-1201.tools.eqiad.wmflabs with local (Exim 4.76)
	(envelope-from <root@tools.wmflabs.org>)
	id 1ZFJDM-0002Lj-K0
	for tools.anagrimes@tools-bastion-01.eqiad.wmflabs; Wed, 15 Jul 2015 09:42:56 +0000

So assuming tools-bastion-01 is arbitrary, tools-mail would need to have a list of all Toolforge instances? Because in this case, the mail was submitted on tools-webgrid-lighttpd-1201 so it's not just that the local hostname gets (incorrectly) appended. With the new DNS structure, the check could be reduced to *.tools.eqiad.wmflabs, but these "extended" hostnames do not appear in the mail addresses. Hmmm.

And /etc/mailname on tools-bastion-01 is (correctly):

scfc@tools-bastion-01:~$ cat /etc/mailname 
tools-bastion-01.tools.eqiad.wmflabs
scfc@tools-bastion-01:~$

Maybe gridengine uses the old hostnames and we need to switch it to the new scheme first?

Rereading the man page for mailname, of course the other approach to try would be to set /etc/mailname to tools.wmflabs.org and see what happens. Issues to look out for:

• Is /etc/mailname only used to qualify mail addresses or (mis)used by a sending/receiving exim to identify itself?

I set /etc/mailname to tools.wmflabs.org, restarted gridengine-master, submitted a job on toolsbeta-master and qstat -j 4 still gave:

[…]
mail_list:                  scfc@toolsbeta-master.toolsbeta.eqiad.wmflabs
[…]

So this path is not a viable solution.

Change 237863 had a related patch set uploaded (by Tim Landscheidt):
Tools: Accept mail for all submit hosts

https://gerrit.wikimedia.org/r/237863

Change 237863 merged by Yuvipanda:
Tools: Accept mail for all submit hosts

https://gerrit.wikimedia.org/r/237863