Distinguish filters as EHLO senders
Using filters in an MTA like Postfix causes swapping between queue and daemon, mostly done on localhost. This gives unclear Received:
headers. To give a hint, allow a host-name
parameter that ends up in the EHLO
command instead of the original one. This may help to give a hint. If it's internal to mail0.example.com
it should be alright to use a non-existing name like axesmtp.mail0.example.com
.