During planned downtime, Salesforce queues inbound emails destined for Email to Apex routing addresses and the email is delivered when the maintenance is complete.

 

During unplanned downtime, inbound emails can be handled 1 of 3 ways depending on the nature of the Salesforce outage and how your Apex Email Service is configured. Unfortunately, Salesforce doesn't provide any official documentation on this and it is largely based on our experience during past events. Because inbound emails don't reach Email to Case Premium during Salesforce downtime, planned, or unplanned, we have no control over what happens to emails during this time.

• In most instances, inbound emails are queued during unplanned downtime just as they are during planned downtime and delivered when service is restored.
• In rare instances, inbound emails fail during unplanned downtime.
  • If you have a "Route Error Emails to This Email Address" value specified, a failure notice along with a copy of the email will be sent to that address.
  • If you do not have a "Route Error Emails to This Email Address" value specified, a failure notice along with a copy of the email sent will be sent to the original sender.