The documentation on governor limits states that:
Email services rejects email messages and notifies the sender if the
email (combined body text, body HTML and attachments) exceeds
approximately 10 MB (varies depending on language and character set).
I just had this happen to me. But although a reject notice was sent to the sender, I didn’t get any notification as the Admin. Is there a way to be notified of emails rejected because they’re too big?
I don’t think we can achieve this through standard salesforce functionality. Alternate approach for this would be auto forward those kind of emails to a email service address to handle those emails by creating tasks and assign to Sys Admins so that they can track and resolve issues. Or simiply configure at Exchange server to autoforward this kind of emails to Sys Admin group.