Email to Case On Demand - Attachment Size Limit Bounce Handling
|Knowledge Article Number||000193653|
The inbound Salesforce Email Server (MTA), currently has governing limits around attachment size and total email size (noted in Help & Training and other Articles).
Based on the size and type of attachment, as well as Email to Case On Demand configurations ('Over Email Rate Limit Action' selection located under Setup | Customize | Cases | Email to Case), the Sender of the email will receive a delivery failure notification from their MTA (Mailer-Daemon notification) indicating that the email could not be delivered. A case will not be created from the email as it will be returned to the sender.
If the inbound message redirected from the Routing Address exceeds 25MB in total (Body/Attachments/HTML/etc.), depending on how the Routing Address is redirecting the email to the Salesforce Email Services Address, either the original Sender of the email, or the Routing Address will receive a Mailer-Daemon bounce.
* Note - due to encoding of emails, total email size when delivered can inflate up to 33%; So in actuality, the attachment size can range around 18MB, depending on other factors of the email.
Prior to the Summer '14 release this maximum limit was 10MB.