One-Click Send enables users to send an envelope for eSignature without needing to go through the various eSignature screens. You can directly send documents to default recipients or Primary Contacts with a single click without configuring additional attachments or recipients. You must have exactly one document in the Notes and Attachments section and a Primary Contact or one recipient in DocuSign Recipients related list. However, One-Click Send for Specific Envelopes enables the users to enable One-Click Send feature for specific envelopes only. To enable this feature, the One-Click Send checkbox in the System Properties must be disabled. Also, you must pass a parameter &oneclick=true in the URL with your envelope Id.

The default text of email subject for the envelopes sent using one click is Document Signature Required, and the email body is defaulted to DocuSign's default Email Body text. Recipient level email templates are picked, but merge fields will not be evaluated. So if templates are used to define recipient level emails, they should not contain any merge fields.