Group email frequently doen's deliver to gmail.com

Group email frequently doen's deliver to gmail.com

For most of the e-mail I can see automatic message like this:

A message could not be delivered to its recipients : <*adres1*>@gmail.com <*adres2*>@gmail.com Group : *@<domain.in.zoho>

========================= Forwarded message =========================

Subject: ***
From: "System Synergia"<add@some.domain.some.where>
Date: Mon, 21 Mar 2022 15:49:22 +0100
To: *@<domain.in.zoho>

------------------------- Contents -------------------------
... and here is coming original messsage.
I've replaced all meaning e-mail addresses.

There is no even any explanation why ot was not delivered,
Where should I look for any details?