Outbound Email Attachment Limits in Lightning Experience and Salesforce Classic

When sending emails from Salesforce to customers or colleagues, you may need to attach multiple files such as contracts, presentations, or documentation.

You may encounter one of the following errors when trying to attach a file to an outbound email.

Salesforce Classic: "The file cannot be larger than 10MB."
Lightning Experience: "0 of 10 files selected"

This can happen when using a Salesforce-integrated email application such as the Email quick action or the Send Email button.

NOTE: This doesn't apply for List Email or Mass Email features.