Email API for SaaS Startups: Ship Notifications Without a Separate Bill
Why young SaaS products bundle transactional email with workspace mail — keys, logs, same domain reputation, and free-tier economics.
Early-stage SaaS teams often pay SendGrid or Resend before they have fifteen employees. If you already need business inboxes for the team, combining human mail and API mail on one authenticated domain simplifies billing and reputation.
What a young product actually sends
- Sign-up confirmations and email verification
- Password resets and security alerts
- Receipts, invoices and failed-payment notices
- Notifications the user asked for: an export is ready, a teammate invited them
How it works on OquMail
Your app sends with one HTTPS request using an API key that belongs to a mailbox on your domain, such as notifications@. Messages are signed with your domain's DKIM key, and every send is logged with the receiving server's response. Keys can be revoked at any time, so give each environment or service its own.
Know the limits before you build
Each mailbox can send up to 250 emails a day, and API sends count toward the same cap as mail your team sends by hand. Each API key also has per-minute and daily limits, and the API answers HTTP 429 with a Retry-After header when one is reached. That comfortably covers transactional mail for an early product; bulk newsletters and cold outreach belong elsewhere. See email API rate limits and fair use.