Integrations

booknslot is deliberately a small-surface plugin: it talks to two external systems and emits one open standard. No proprietary SDKs, no vendored cloud dependencies.

WordPress wp_mail() (email)

Every email booknslot sends — OTP verification codes, booking-received notifications, approval requests, approval / rejection emails — goes through WordPress’s built-in wp_mail().

Setup

There is no booknslot-side mail setup. You pick the SMTP provider, you install the corresponding plugin, booknslot picks it up automatically.

1. Install any reliable transactional-email plugin: WP Mail SMTP, Fluent SMTP, Post SMTP, or Easy WP SMTP all work. Configure it with your provider (SendGrid, Postmark, Amazon SES, your Gmail Workspace account — whichever you already use).
2. Send a test email through the SMTP plugin’s test page to confirm deliverability.
3. In booknslot: Booking Manager → Settings → Email delivery — optionally set a custom “From email” and “From name” that will apply only to booknslot’s emails (other plugins keep their own From addresses untouched).
4. Use the Send test email button on the same panel to confirm booknslot’s path works end-to-end.

Why no built-in API integration?

Earlier versions of booknslot shipped a direct Resend HTTP integration. That was removed in v1.4.4 — it duplicated what every SMTP plugin already does well, locked customers into one vendor, and made the plugin harder to deploy on hosts that already had an SMTP layer. Routing through wp_mail() means whatever you (or your client) already trust for transactional email continues to work.

LemonSqueezy (licensing + distribution + updates)

LemonSqueezy is the merchant of record and license server. It handles:

1. Customer buys on booknslot.com → LemonSqueezy charges the card.
2. LemonSqueezy emails the customer a unique license key + a download link for the .zip.
3. The customer installs the .zip and pastes the license key into Booking Manager → License.
4. The plugin validates the key against LemonSqueezy’s API.
5. A daily WordPress cron revalidates the key. A 7-day grace period covers transient LS API outages.
6. Self-hosted updates (v1.6.0+) — a separate daily cron polls booknslot.com/wp-update.json for new releases. When a newer version is available, WordPress shows the standard “Update available” notice on the Plugins page; one click downloads the license-gated zip and wp_mail()’s unzipper installs it.

Refunds, upgrades, and license transfers all happen inside the LemonSqueezy customer portal.

iCal .ics calendar attachments

When a booking is approved (auto-confirmed or maintainer-confirmed), the confirmation email includes a standards-compliant .ics file. Apple Calendar, Outlook, Google Calendar, and every other major calendar client parse it and let the booker add the event with one click.

No separate setup — this works out of the box. The .ics generator is hand-written per RFC 5545 inside the plugin (no external library).

What is NOT an integration

These are deliberately not shipped, even though the URLs to fake them would be easy enough:

• Direct Stripe / WooCommerce deposits. booknslot does not charge bookers anything at booking time. If you need to take a deposit, point the post-booking confirmation email at a separate payment link.
• Google Calendar 2-way sync. The .ics attachment is a one-way push (booker adds it to their calendar). True bidirectional sync — where the maintainer’s Google Calendar conflicts also block our slots — is on the roadmap.
• Zapier / generic webhooks. Not available yet. The REST API under booknslot/v1/ is polled-readable from the site owner’s end if you want to wire automations on your side.

If any of those become must-have for your use case, contact us at hello@booknslot.com — we track requests against the roadmap.