getting email message, that says "Documents sent for signature could not be delivered"

Generally this means the recipient's email server is sending back a fatal error to DocuSign that it could not deliver the documents to the specified email address. Please verify that you have entered the email address correctly. Beyond that, can you verify emails you send directly (not via DocuSign) reach the intended recipient? Is the recipient internal to your company or external? The email server may have blacklisted DocuSign emails. You can ask the recipient to have thier IT department whitelist (https://www.docusign.com/trust/security/features-configurations) DocuSign domains and IP addresses .

Regards.