If the finalization email cannot be delivered to the copy recipients, it is usually because the size exceeds the max 7.5 MB of one or more of the documents. Read more about file size here.
If a file cannot be delivered to copy recipients, the creator of the case file will receive an email from Penneo informing them that the finalization email could not be delivered. In this case, the files need to be distributed in another way. The signers will however be able to access their documents by logging in to app.penneo.com.