Billing & Credits

Ark uses a prepaid credit system for billing. You purchase credits in advance, and credits are deducted as you send emails. This applies to both the REST API and SMTP.

Pricing

Metric	Cost
Per 1,000 emails	$0.50
Per email	$0.0005

Per recipient billing: You’re charged per recipient, not per API call. An email to 3 recipients counts as 3 emails.

Example Costs

Emails	Cost
1,000	$0.50
10,000	$5.00
100,000	$50.00
1,000,000	$500.00

Welcome Credit

All new organizations receive $5.00 in welcome credits - enough to send approximately 10,000 emails. This lets you fully evaluate Ark before adding payment details.

How Credits Work

Reserve

When you send an email, credits are reserved immediately before the email is processed.

Send

The email is sent to recipients.

Confirm or Refund

If sending succeeds, the reserved credits are deducted. If sending fails immediately (e.g., Postal rejection), credits are refunded.

Bounces are still charged: If an email is accepted by our system but later bounces (e.g., mailbox full, user doesn’t exist), you’re still charged. This is standard practice as the email was transmitted successfully.

Balance Checks

REST API

Balance is checked when you call the send endpoint. If insufficient, you’ll receive a 402 response:

{
  "success": false,
  "error": {
    "code": "insufficient_balance",
    "message": "Insufficient credit balance",
    "suggestion": "Add credits at https://arkhq.io/org/billing"
  }
}

SMTP

Balance is checked when the DATA command completes. If insufficient:

452 Insufficient credit balance. Add credits to continue.

Auto-Recharge

Enable auto-recharge to avoid interruptions:

Setting	Description	Default
Enabled	Whether auto-recharge is active	Off
Threshold	Balance that triggers recharge	$2.00
Amount	How much to add when triggered	$10.00

When your balance drops below the threshold, we automatically charge your saved payment method.

Recommended settings: For production workloads, enable auto-recharge with a threshold that covers at least one day of typical sending volume.

Fail-Open Design

Ark’s billing system is designed to fail open - if our billing service is temporarily unavailable, emails are accepted rather than rejected. This ensures:

Your email sending isn’t interrupted by transient billing issues
High availability for critical transactional emails
You’re only charged for emails we can successfully bill

If the billing system is down, we queue billing records and process them when service is restored. You may see delayed balance updates in rare cases.

Managing Your Balance

Check Balance

View your current balance at arkhq.io/org/billing.

Add Credits

Go to Billing in your dashboard
Click Add Credits
Select an amount ( $5,$ 10, $20,$ 50, or $100)
Complete payment via Stripe

Transaction History

View all billing transactions in your dashboard:

Credit purchases
Auto-recharge events
Usage charges (per API call or SMTP session)
Refunds

Payment Methods

We accept:

Credit cards (Visa, Mastercard, American Express)
Debit cards

Payment is processed securely via Stripe. Card details are never stored on our servers.

Managing Cards

Add cards via the Billing page
Set a default card for auto-recharge
Remove cards anytime via Stripe Customer Portal

Invoices & Receipts

Access invoices and receipts through the Stripe Customer Portal:

Go to Billing in your dashboard
Click View Invoices or Stripe Portal
Download PDF invoices for any transaction

Error Handling

Billing Errors

Error	HTTP Status	Cause	Solution
`billing_not_configured`	402	No billing account	Set up billing in dashboard
`insufficient_balance`	402	Balance too low	Add credits
`billing_error`	500	System error	Retry (fails open)

SDK Handling

Python
Node.js

import ark
from ark import Ark

client = Ark()

try:
    email = client.emails.send(
        from_="[email protected]",
        to=["[email protected]"],
        subject="Hello",
        html="<p>Hello!</p>"
    )
except ark.BadRequestError as e:
    if e.code == "insufficient_balance":
        # Balance too low - add credits or wait for auto-recharge
        print(f"Add credits: {e.suggestion}")

import Ark from 'ark-email';

const client = new Ark();

try {
  await client.emails.send({
    from: '[email protected]',
    to: ['[email protected]'],
    subject: 'Hello',
    html: '<p>Hello!</p>',
  });
} catch (error) {
  if (error instanceof Ark.BadRequestError && error.code === 'insufficient_balance') {
    // Balance too low - add credits or wait for auto-recharge
    console.log(`Add credits: ${error.suggestion}`);
  }
}

FAQ

What happens if my balance runs out mid-batch?

If you’re sending a batch and your balance runs out, emails that haven’t been processed yet will fail with insufficient_balance. Successfully queued emails will still be sent.

Do sandbox emails cost credits?

Yes, sandbox emails count against your credit balance. The welcome credit covers extensive sandbox testing.

Can I get a refund?

Credits are non-refundable but never expire. Contact support for special circumstances.

How do I estimate my costs?

Multiply your monthly email volume by $0.0005. For example:

50,000 emails/month = $25/month
500,000 emails/month = $250/month

Is there a minimum purchase?

The minimum credit purchase is $5.00 (10,000 emails).

Next Steps

Set Up Billing

Configure billing in your dashboard

Send Your First Email

Start sending with your welcome credits

Getting Started

Guides

Concepts

Reference

Pricing

Example Costs

Welcome Credit

How Credits Work

Balance Checks

REST API

SMTP

Auto-Recharge

Fail-Open Design

Managing Your Balance

Check Balance

Add Credits

Transaction History

Payment Methods

Managing Cards

Invoices & Receipts

Error Handling

Billing Errors

SDK Handling

FAQ

Next Steps

Set Up Billing

Send Your First Email

Getting Started

Guides

Concepts

Reference

​Pricing

​Example Costs

​Welcome Credit

​How Credits Work

​Balance Checks

​REST API

​SMTP

​Auto-Recharge

​Fail-Open Design

​Managing Your Balance

​Check Balance

​Add Credits

​Transaction History

​Payment Methods

​Managing Cards

​Invoices & Receipts

​Error Handling

​Billing Errors

​SDK Handling

​FAQ

​Next Steps

Set Up Billing

Send Your First Email

Pricing

Example Costs

Welcome Credit

How Credits Work

Balance Checks

REST API

SMTP

Auto-Recharge

Fail-Open Design

Managing Your Balance

Check Balance

Add Credits

Transaction History

Payment Methods

Managing Cards

Invoices & Receipts

Error Handling

Billing Errors

SDK Handling

FAQ

Next Steps