Zoho Calendar's own notification domain (noreply@eu-sender.zohocalendar.com) bounces at Apple and is spam-filtered by Zoho Mail itself

Hi all, I'm really hoping there will be some solutions from this because despite a lot of emails, support from Zoho has not been forthcoming. I am posting as a single defect report, since both symptoms trace to the same sending domain.

Summary: Zoho Calendar sends invitations and reminders from noreply@eu-sender.zohocalendar.com / eu-notifications.zohocalendar.com, and not from my own account's verified custom domain; this is regardless of the Calendar DKIM being configured and verified. This is issue is producing two separate failures:

Outbound Invites — delivery to iCloud-hosted recipients fails. Invitations to an iCloud-hosted address have hard- and soft-bounced repeatedly since early September, despite a verified Calendar DKIM record on the sending domain. There has been one instance where this was successful immediately after updating the DKIM, but the issue has since returned and no amendments or updates to the DKIM have solved it since. Ordinary emails from the my account to the same Apple recipient delivers without issue; the issue only affects Calendar-originated invites. The "undelivered" status is not sent to my account as an email - instead, there is a tiny orange button inside the event that shows the fault - inside this UI is a brief explanation and where the soft- and hard- bounce reject messages are displayed.
Inbound Reminder Notifications — my account's own Calendar reminders are filtered to Spam - at all times. Reminder emails for my account's own events, which are being sent to me from the same noreply@eu-sender.zohocalendar.com address as the above fault, are landing directly in my own Zoho Mail Spam folder — despite my account having full and verified SPF, DKIM and DMARC passes in place. A ToDo task reminder sent the same week from my account's custom domain was not filtered and was sent successfully to the inbox; this isolates the fault to the Zoho Calendar notification pipeline specifically rather than Zoho Mail's spam engine generally.

Why this matters beyond one account: Zoho's own deliverability guidance states that a "no-reply@" sending address is more likely to be spam-filtered, and recommends sending from the organisation's own domain instead.

noreply@eu-sender.zohocalendar.com is exactly the pattern that guidance warns against — so this isn't a one-off misconfiguration, it's Zoho Calendar's default sending behaviour contradicting Zoho's own published standard, for every account relying on Calendar DKIM to fix deliverability.

Already tried: Calendar DKIM verified and confirmed (both independently and by Zoho Support); confirmed via Support that this does not change the sending address invitations/reminders use. Raised as ticket ## 2794803 ## — currently unresolved - and the latest response has suggested that I remove Google Meet - this is not only irrelevant advice, it is obsolete because my account does not have the Google Meet integration enabled.

I have a Filter in place to redirect all reminders from the noreply address away from Spam and into the Inbox; this is by no means a solution - the solution is for Zoho to rectify the issue that should not even be present in the first place.

Question for Zoho / the community: Is there any existing way to have Calendar invitations and reminders sent from, and signed as, the account's own verified domain rather than the shared notification domain? And has anyone else found their own Calendar reminders landing in Spam?