Set up email delivery

Download mode needs nothing. Email mode sends the EPUB straight to your Kindle — it takes ~10 minutes to set up, once.

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Why a relay? Browsers can't send email (no SMTP). The relay is a stateless function that forwards the EPUB through your mailbox to your @kindle.com address. It stores nothing, and nothing ever reaches the developer.

Step 1

Deploy your own relay on Netlify (free)

Deploy to Netlify

The button deploys the project (it reads netlify.toml, base directory server). Or manually: sign in at app.netlify.com, then drag the server/ folder onto the Deploys area, or connect the Git repo with Base directory = server.

Step 2

Get an email app password

You need SMTP credentials for your mailbox — always an app password, never your normal login password.

Provider	SMTP host / port	App password
Gmail	`smtp.gmail.com` / `465`	myaccount.google.com/apppasswords (2FA required)
Fastmail	`smtp.fastmail.com` / `465`	Settings → Privacy & Security → App Passwords → new, access IMAP/SMTP
iCloud+	`smtp.mail.me.com` / `587`	appleid.apple.com → App-Specific Passwords
Other	your provider's SMTP	your provider's app-password page

Step 3

Set the environment variables on Netlify

Site configuration → Environment variables → add these (scope: Functions):

SMTP_HOST=smtp.gmail.com
SMTP_PORT=465
SMTP_SECURE=true
SMTP_USER=you@example.com
SMTP_PASS=your_app_password
SMTP_FROM=you@example.com
RELAY_TOKEN=a-long-random-string

RELAY_TOKEN is optional but recommended — it stops anyone else using your public endpoint. Generate one with:

node -e "console.log(require('crypto').randomBytes(24).toString('base64url'))"

Then Deploys → Trigger deploy — env-var changes only apply on a new deploy. To check it's live, open https://<your-site>.netlify.app/.netlify/functions/send in a browser: it should say “Method not allowed” (not a 404).

Step 4

Approve your sender on Amazon (the step people forget)

Amazon silently drops documents from addresses you haven't approved.

Open Manage Your Content and Devices → Preferences → Personal Document Settings (use your country's Amazon): .com · .co.uk · .fr · .de · .ca
Under Approved Personal Document E-mail List → Add a new approved e-mail address → enter your SMTP_FROM address → Add.
On the same page, under Send-to-Kindle E-Mail Settings, copy your device's …@kindle.com address.

Step 5

Configure the extension

Extension → Settings → Send by email, then fill:

Kindle address — the …@kindle.com from step 4.3
Relay URL — https://<your-site>.netlify.app/.netlify/functions/send
Relay token — the RELAY_TOKEN from step 3 (if you set one)

Save, open an article, hit Send to Kindle — it arrives in a few minutes. 🎉

Troubleshooting

Symptom	Cause / fix
`Relay: 404`	Wrong relay URL — it must end with `/.netlify/functions/send`
`Relay: 401`	Token mismatch — the extension's token must equal `RELAY_TOKEN`
`Invalid login` (500)	Wrong `SMTP_USER`/`SMTP_PASS` — use an app password
`ECONNREFUSED 127.0.0.1`	`SMTP_HOST` not set, or you didn't redeploy after adding env vars
Sent OK but nothing on the Kindle	Sender not on Amazon's approved list, or wrong `@kindle.com` address