Mail rejected for no DNS

[#1]

I realise there's a lot of spoof email about, but totally rejecting mail because it's sent From: a subdomain that's not set up properly on DNS can be a bit harsh. I booked a table for a pub lunch and the confirming email got rejected as follows:

Status: 550
Action: failed
Last-Attempt-Date: 13 Mar 2024 12:33:59 GMT
Diagnostic-Code: #5.1.8 Domain of sender address <booking@bookings.vintageinn.co.uk> does not exist
Remote-MTA: dns; mx.avasin.plus.net

By all means flag it as spam but don't completely suppress useful mail.

Of course most people won't know this is happening, I can see it because my mail goes though an intermediate forwarder that catches the rejection and sends it to me instead of the original source.

[#2]

Mail passing through a forwarding server is invariably a nightmare.  Does the forwarding service implement SRS?

The DMARC policy for that domain appears to indicate that mail should be treated as having being sent by the parent domain ... so may be something else is 'in play' here.  See Network Tools: DNS,IP,Email (mxtoolbox.com)

First line support are now handling false positive SPAM issues - can you please raise a support issue with the call centre ... if that does not work, please report that here and I will raise the matter within the superuser discussion group.