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Attachment size limit for On-Demand Email-to-Case

게시 일자: Apr 30, 2026
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Issue
 
The inbound Salesforce Email Server (MTA — Mail Transfer Agent, the server responsible for routing inbound email) has governing limits around attachment size and total email size for On-Demand Email-to-Case.

When an inbound email exceeds the size limit, Salesforce does not create a Case from the email. Instead, depending on configuration, the original sender or the routing address receives a delivery failure notification (Mailer-Daemon bounce) from their mail server.
 

On-Demand Email-to-Case Configuration

On-Demand Email-to-Case configuration settings, including the Over Email Rate Limit Action, can be accessed via:

In Salesforce Classic: Setup | Build | Customize | Cases | Email-to-Case | On-Demand Service | Failure Response Settings
 
In Lightning Experience: Gear icon | Setup | Platform Tools | Feature Settings | Service | Email-to-Case | On-Demand Service | Failure Response Settings


Notes:

  • Based on the size and type of attachment, as well as On-Demand Email-to-Case configurations, the sender receives a delivery failure notification (Mailer-Daemon notification) indicating the email could not be delivered.
  • A Case is not created from the email — the email is returned to the sender.
솔루션

Attachment Size Limits for On-Demand Email-to-Case

This section describes the inbound email size limits enforced by Salesforce for On-Demand Email-to-Case. Understanding these limits helps administrators configure routing and set expectations for senders whose emails are bounced.
When the inbound message redirected from the routing address exceeds 35 MB in total (Body, Attachments, HTML, etc.), either the original sender or the routing address receives a Mailer-Daemon bounce, depending on how the routing address redirects email to the Salesforce Email Services Address.

Size Limit Details

  • Due to email encoding, total email size when delivered can inflate by up to 33%. In practice, the effective attachment size limit is approximately 25 MB, depending on other factors in the email.
  • Before the Summer '14 release, the maximum limit was 10 MB.
  • Before the Winter '21 release, the maximum limit was 25 MB.
  • The current maximum limit is 35 MB.
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