IDR: Maximum number of invoice images on single email

Summary:

Is there a maximum number of invoice images that can be sent on a single email when using IDR?

Content (required):

We are implementing IDR and would like to know if there is a maximum number of invoice image attachments that can be sent on a single email.

Version (include the version you are using, if applicable):

23B

Code Snippet (add any code snippets that support your topic, if applicable):