[Exim] use of _ in HELO... again

I've run into a problem where I've been told by management to break the RFCs
and allow the use of _ in an HELO.

I sent them the relative RFCs about this. They came back with "RFCs aren't
standards". The people we're having problems with have more problems.
(checked their domain through dnsreport.com)

Anyone have any thoughts of how to combat stupid management?

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Lab tests show that use of micro$oft causes cancer in lab animals