> On 19/01/2024 00:33, Randolf Richardson, Postmaster via mailop wrote:
> >     The blacklists seem to be blocking mostly the ones that send 
> > directly from @<something-strange>.onmicrosoft.com addresses, which 
> > should make filtering easy if we can confirm for certain that no 
> > legitimate eMail has these as the sender -- that is, not in the 
> > "Return-Path:" header and not in the "From:" header.
> 
> I have a legitimate email today from @example.onmicrosoft.com (both
> envelope sender and From: header) that is a cross-organisation meeting
> invite. Normally all of their email uses their domain but some Microsoft
> software is using this internal domain for meeting invites.
> 
> Indiscriminate blocking is going to unexpectedly reject real email.

        This is an important observation -- thanks for sharing it.

        Unfortunately, this ultimately means that there's one less avenue of 
defense for mail server operators, and it almost feels like an effort 
on Microsoft's part to make their onmicrosoft.com domain gradually 
immune to filters. :(

-- 
Postmaster - postmas...@inter-corporate.com
Randolf Richardson, CNA - rand...@inter-corporate.com
Inter-Corporate Computer & Network Services, Inc.
Vancouver, British Columbia, Canada
https://www.inter-corporate.com/


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