DocSend comes prebuilt with a number of different merge options, including an Outreach 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 Outreach as your email service.
When you're done configuring your link options, click Create Link. You can copy your link at any time from the All Links section at the bottom of your document page.
After you've copied your link, paste it directly into Outreach 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.