DocSend comes prebuilt with a number of different merge options including a Yesware integration.
To create a Mail Merge Link for any of your documents, click on the More arrow on any document page and select the Mail Merge Link option.
From here, name the Campaign associated with your blast and select Yesware as your email service.
When you're done configuring your link options, then click Create Link. You can copy your link at any time from the All links section at the bottom of your document's page.
After you've copied your link, paste it directly into Yesware and it will substitute the email field parameter with the emails in your blast.
We recommend creating a hyperlink in your email with your Mail Merge Link, that way the full link will remain hidden from your recipient.