Tickets are being suspended with the cause Automatic email processing failed:
This can be caused by a mismatch in user organization information.
To see if this is the case, open the user profile of the user listed in the FROM field of the email in the Support interface and copy their user ID from the address bar:
Take this ID and use it in the URLs listed below. Replace USER_ID_HERE with the user ID obtained from the user profile and replace the value of SUBDOMAIN with your account's subdomain:
In the first of these URLs, look for the organization_id value:
Make sure that the same organization_id value appears within the list of memberships in the second URL:
This will provide you with a more readable output of the data returned by these URLs.
If it is not present, remove the organization from the user in the Support interface and re-add it to bring these back into alignment.
If the same value is present in both of these URLs, then email processing is failing for a different reason so contact Zendesk Customer Support.
For more information on ticket suspension, see the article: Causes of ticket suspension.