DocSend comes prebuilt with a number of different merge options including a ToutApp 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 ToutApp as your email service of choice where you'll be using the link.
When you're done configuring your link options, click the green button to create your link. You can copy the link at any time from the All Links section at the bottom of your document.
After you've copied your link, paste it directly into ToutApp 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.