This knowledge base article is only applicable if the destination server is unreachable and the customer does not have the continuity service enabled.

We will spool (Retry) by default: inbound emails for 48 hours

We will spool (Retry) email for a maximum of 7 days if the SMTP relay check is disabled

Yes, there is technically a way to create an Auto reply as a workaround here, but this is not something we support.