Connecting Resend and creating an API key

What is Resend?

Resend is an email delivery service for developers. When Presumption needs to send an outreach email or a campaign, it hands the message to Resend, which delivers it to the recipient's inbox and handles all the behind-the-scenes work that keeps mail out of spam — authentication, retries, and delivery tracking.

You need it because Presumption doesn't have its own mail server for your domain. Connecting your Resend account lets your automations send email from an address you actually own, like hello@yourcompany.com.

Step 1 — Create a Resend account

Go to resend.com/signup and sign up with your work email. There's a free tier that's enough to test and send your first campaigns.

Step 2 — Create an API key

Once you're signed in to Resend:

1. 1
   Open API keys

   In the left sidebar, click API Keys.

2. 2
   Create a new key

   Click the Create API Key button.

3. 3
   Name it and pick full access

   Give it a name like "Presumption". Choose Full access so Presumption can send email and check your verified domains. Then click Create.

4. 4
   Copy the key

   Resend shows the key once, starting with re_. Copy it right away — you won't be able to see it again. You'll paste it into Presumption next.

Step 3 — Verify your sending domain

Email can only come from a domain you own and have verified in Resend. This proves to inbox providers that you're allowed to send from that address.

1. 1
   Open Domains

   In the Resend sidebar, click Domains, then Add Domain.

2. 2
   Enter your domain

   Use the domain you send email from, like yourcompany.com.

3. 3
   Add the DNS records

   Resend gives you a few DNS records (SPF, DKIM, and a return path). Add them to your domain's DNS at your registrar or DNS provider — Google Domains, Cloudflare, Namecheap, etc.

4. 4
   Wait for verification

   DNS can take a few minutes to a few hours to update. Once Resend shows Verified, you're ready.

Step 4 — Connect it in Presumption

1. 1

   Open Settings → Connections in your dashboard.

2. 2

   Find Resend and click Add key.

3. 3

   Paste the re_... API key you copied in Step 2.

4. 4

   Enter the address your emails should come from — it must be on the domain you verified in Step 3, for example Your Company <hello@yourcompany.com>.

5. 5

   Click Save key. Presumption checks the key against Resend and connects your account.

Tip — use domain warming

When you first connect Resend, Presumption offers to turn on domain warming. This keeps your daily sends low at first and raises the limit gradually, which builds a good sender reputation so your emails land in the inbox instead of spam. You can turn it on or off anytime in the same Resend connection panel.