Mailgun Transactional Email
Send transactional email through Mailgun without losing bounce and complaint state.
What it adds
A Mailgun delivery path bound to the correct region and sending domain, with durable suppression and event handling.
What your agent is told to do
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What your agent is told to do
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Put Mailgun behind the app's existing mail layer as one adapter. It is an alternative to the other transactional email integrations, not an addition; whichever adapter is in place, the template contract and suppression handling above it are unchanged.
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Bind the region and sending domain in server-side configuration and validate at startup that they are consistent. A credential issued in one region will simply not work against another, and the failure looks like an authentication problem rather than a configuration one.
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Check the suppression state for an address before a message is queued, not after the provider rejects it, so bouncing and complaining addresses stop consuming send attempts.
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Send from the app's background-job system keyed on a stable per-message identifier, and store the provider's identifier on the record for support diagnostics.
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Do not retain full message bodies for diagnostics. Keep the recipient, the message type, the timestamps, the delivery state, and the provider identifier, which are enough to answer a support question without holding a copy of every reset link the app has ever sent.
Edge cases it handles
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Edge cases it handles
8- Region and sending domain must match the credential in use. Validate the combination at startup and fail loudly, rather than letting every send fail at runtime with a misleading authentication error.
- Event webhooks arrive on a public endpoint, are retried by the provider, and can arrive out of order. Verify their authenticity, apply them idempotently, and never let a replayed older event overwrite a newer delivery state.
- An address on the suppression list must be filtered before the message is queued. Queueing mail that will be rejected wastes attempts, muddies delivery metrics, and hides the real problem from the user whose address is broken.
- A background job retried after a timeout must reconcile against the existing message rather than sending a second copy. Key it on a stable identifier.
- Retaining full message bodies for diagnostics turns the log store into a source of live credentials and personal data. Keep metadata and delivery state only, with a defined retention period.
- Transactional mail must not be blocked by marketing unsubscribe state, and marketing mail must not be routed through this path to bypass it.
- Rate limits and transient provider errors must be distinguished from permanent rejections, backing off on the former and stopping immediately on the latter.
- Non-production environments must suppress delivery or redirect all recipients to a fixed internal address by default, so a seeded data set cannot mail real people.
Definition of done
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Definition of done
9- Region and sending domain are validated at startup against the credential in use.
- Suppressed addresses are filtered before a message is queued.
- Event webhooks are authenticated, idempotent, and cannot regress delivery state.
- Every message record carries the provider identifier and its delivery state.
- Message bodies are not retained; metadata is kept under a defined retention period.
- Retried jobs never produce a duplicate email.
- Non-production environments cannot deliver to real recipients.
- The feature matches the existing design system.
- No existing functionality is broken.
Related features
Firebase Cloud Messaging
Firebase Cloud Messaging
Deliver push through Firebase with registration tokens that stay valid as devices change.
What it does
A Firebase-backed push channel with server-side token lifecycle management, consistent payload handling across platforms, and safe handling of the routes a notification opens.
How it works
- 1 Store one record per device registration, tied to the account signed in at the time, the platform it came from, and when it was last confirmed working, and let one account hold many of them.
- 2 Send from the app's existing background-job system with the provider credentials held server-side, and treat every send as a job that can be retried rather than work done inline during a request.
- 3 Decide, per notification type, whether the payload is meant to be displayed by the platform or handled by the app, and keep that decision the same on every platform. The same event behaving as a visible alert on one platform and a silent update on another produces bugs nobody can reproduce.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/firebase-cloud-messaging
OneSignal Push Notifications
OneSignal Push Notifications
Send push notifications to the right devices, with user preferences respected.
What it does
A push delivery path through OneSignal covering subscription registration, audience targeting, per-channel preferences, and delivery outcomes recorded against the app's own records.
How it works
- 1 Find the events the app already notifies on by email or in-app, and treat push as another channel for those same events rather than a separate notification system with its own triggers.
- 2 Record the link between a push subscription and an account on the server, established at sign-in and severed at sign-out, so a device that changes hands does not keep receiving the previous user's notifications.
- 3 Hold the provider credentials server-side and send every message from the app's existing background-job system, so a slow or failing provider never blocks a web request.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/onesignal-push-notifications
Resend Transactional Email
Resend Transactional Email
Send application email through Resend with verified domains and tracked delivery.
What it does
A Resend delivery path with domain verification gating production sends, controlled attachments, and recorded delivery events.
How it works
- 1 Put Resend behind the app's existing mail layer as one adapter. This entry is an alternative to the other transactional email integrations rather than a companion to them; the mail layer, template contract, and suppression handling stay the same whichever adapter is in place.
- 2 Gate production delivery on a verified sending domain. Until verification is confirmed, keep the app in a mode that redirects or suppresses delivery rather than sending from an unverified address into spam folders.
- 3 Send from the app's background-job system, keyed on a stable per-message identifier, and store the provider's identifier on the record as soon as it is returned.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/resend-transactional-email
How it works
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Copy the link
Grab the Markdown instruction URL for this feature.
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Give it to your AI
Paste it into Claude Code, Cursor, v0, Lovable — whatever you build with.
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It inspects, then implements
Your agent reads your existing app first, then adds the feature to fit it.
Works with your stack
These instructions are written to adapt. They tell the agent to detect your framework, match your existing design system, and reuse what you already have — rather than assuming a particular stack.
Need it tighter than that? Customize the feature and tell it exactly what you're running.