Nipa sends transactional email through a pluggable sender. The sender layer (internal/mail) supports SMTP, the SendGrid v3 REST API, the Scaleway Transactional Email REST API and a generic HTTP JSON sender that adapts to any REST provider; delivery is durable through an outbox (see Delivery model).

Status: complete. The sender layer, configuration, the durable outbox, the merge request notification wiring and the delivery admin surface (inspection and redelivery) are implemented.

Choosing a sender

EMAIL_SENDER selects the transport:

Value	Transport
`off`	Default. No email is sent; the notification seam is unwired.
`log`	Writes rendered messages to the server log. Development and tests.
`smtp`	Any provider with an SMTP endpoint (SES, Mailgun, Postmark, Gmail, …).
`sendgrid`	SendGrid v3 API (`POST /v3/mail/send`) with an API key.
`scaleway`	Scaleway Transactional Email REST API with a secret key and project.
`http`	Generic REST sender: configurable endpoint, method, headers and body.

EMAIL_FROM is required by every active sender except log and accepts either [email protected] or Nipa <[email protected]>. EMAIL_REPLY_TO is optional. EMAIL_BASE_URL is the public web UI URL used for deep links in notification emails (for example https://nipa.example.com).

SMTP

EMAIL_SENDER: smtp
EMAIL_FROM: 'Nipa <[email protected]>'
EMAIL_SMTP_HOST: smtp.example.com
EMAIL_SMTP_PORT: 587            # 0 = 587/465/25 for starttls/ssl/none
EMAIL_SMTP_USERNAME: mailer
EMAIL_SMTP_PASSWORD: secret
EMAIL_SMTP_TLS: starttls        # starttls | ssl | none

starttls upgrades the connection on the submission port, ssl dials with implicit TLS (port 465) and none speaks plain SMTP (port 25, local relays). EMAIL_SMTP_INSECURE_SKIP_VERIFY: true accepts self-signed certificates and should stay off outside development. Authentication uses AUTH PLAIN; the Go SMTP client refuses to send credentials over an unencrypted connection to a non-local host.

Provider notes:

Amazon SES — SMTP credentials from the SES console, host email-smtp.<region>.amazonaws.com, port 587, starttls.
Gmail / Google Workspace — smtp.gmail.com, port 587, starttls, an app password.
Mailgun / Postmark — smtp.mailgun.org / smtp.postmarkapp.com, port 587, the provider’s SMTP credentials.

SendGrid

EMAIL_SENDER: sendgrid
EMAIL_FROM: 'Nipa <[email protected]>'
EMAIL_SENDGRID_API_KEY: SG.xxxxx
# EMAIL_SENDGRID_ENDPOINT: https://api.sendgrid.com   # override for tests

Messages carry plain-text and HTML parts; Message-ID, In-Reply-To and References are forwarded as personalization headers so notification threads stay grouped in the recipient’s mail client.

Scaleway

EMAIL_SENDER: scaleway
EMAIL_FROM: 'Nipa <[email protected]>'
EMAIL_SCALEWAY_API_KEY: <secret key>   # TransactionalEmailFullAccess
EMAIL_SCALEWAY_PROJECT_ID: <project uuid>
# EMAIL_SCALEWAY_REGION: fr-par          # default
# EMAIL_SCALEWAY_ENDPOINT: https://api.scaleway.com   # override for tests

The sender posts to the regional POST /transactional-email/v1alpha1/regions/{region}/emails endpoint with the secret key as X-Auth-Token. EMAIL_FROM must use a domain verified in the configured Scaleway project. Plain-text and HTML parts map to text/html; Reply-To, Message-ID, In-Reply-To and References travel as additional_headers so notification threads stay grouped in the recipient’s mail client.

Generic HTTP

http posts a rendered template per recipient to any REST provider. The template receives .From, .FromName, .FromEmail, .ReplyTo, .To (list), .ToHeader (comma-joined), .Subject, .Text, .HTML, .MessageID, .InReplyTo and .References, plus a json helper and the standard urlquery helper. EMAIL_HTTP_HEADERS is a JSON object of extra request headers.

The default body is provider-neutral:

{"from":"…","from_email":"…","to":["…"],"subject":"…","text":"…","html":"…"}

Provider examples:

Resend

EMAIL_SENDER: http
EMAIL_HTTP_ENDPOINT: https://api.resend.com/emails
EMAIL_HTTP_HEADERS: '{"Authorization":"Bearer re_xxxxx"}'
EMAIL_HTTP_BODY_TEMPLATE: '{"from":{{json .FromEmail}},"to":{{json .To}},"subject":{{json .Subject}},"text":{{json .Text}},"html":{{json .HTML}}}'

Postmark

EMAIL_SENDER: http
EMAIL_HTTP_ENDPOINT: https://api.postmarkapp.com/email
EMAIL_HTTP_HEADERS: '{"X-Postmark-Server-Token":"xxxxx"}'
EMAIL_HTTP_BODY_TEMPLATE: '{"From":{{json .FromEmail}},"To":{{json .ToHeader}},"Subject":{{json .Subject}},"TextBody":{{json .Text}},"HtmlBody":{{json .HTML}}}'

Brevo

EMAIL_SENDER: http
EMAIL_HTTP_ENDPOINT: https://api.brevo.com/v3/smtp/email
EMAIL_HTTP_HEADERS: '{"api-key":"xxxxx"}'
EMAIL_HTTP_BODY_TEMPLATE: '{"sender":{"email":{{json .FromEmail}}},"to":[{"email":{{json .ToHeader}}}],"subject":{{json .Subject}},"textContent":{{json .Text}},"htmlContent":{{json .HTML}}}'

Mailgun (form-encoded)

EMAIL_SENDER: http
EMAIL_HTTP_ENDPOINT: https://api.mailgun.net/v3/mg.example.com/messages
EMAIL_HTTP_METHOD: POST
EMAIL_HTTP_CONTENT_TYPE: application/x-www-form-urlencoded
EMAIL_HTTP_HEADERS: '{"Authorization":"Basic <base64 of api:key>"}'
EMAIL_HTTP_BODY_TEMPLATE: 'from={{urlquery .FromEmail}}&to={{urlquery .ToHeader}}&subject={{urlquery .Subject}}&text={{urlquery .Text}}'

Log

EMAIL_SENDER: log renders and logs messages without sending them. Useful for local development and for the test suite.

Delivery model

Email delivery is durable: notification events render one message per recipient and enqueue a row in the email_deliveries outbox in the same request that landed the change. A background dispatcher claims due rows, sends them through the configured sender with bounded retries and exponential backoff, and records delivered/failed state with the last error.

Notifications

Merge request events produce email to the participants: mr.created, mr.ready_for_review, mr.review_requested, mr.review_submitted, mr.comment_created, mr.synchronized, mr.merged, mr.closed, mr.reopened and failed mr.check_reported reports. The recipient set is the author, the requested reviewers, the assignees and the commenters; the actor, deleted users, users without a valid email address and users who disabled notify_email in their profile are skipped, duplicates collapse and one event fans out to at most 200 recipients. Each message carries a deep link to the merge request when EMAIL_BASE_URL is set; the first message a recipient gets about a merge request uses a per-recipient thread Message-ID that later messages reference with In-Reply-To/References, so mail clients group the conversation.

Inspecting and redelivering

Project admins can inspect the outbox and retry deliveries:

GET /api/v1/orgs/{org}/projects/{project}/emails/deliveries — newest first, filters state, keyset after cursor and limit (default 50, max 200); the response carries next_cursor when a next page exists.
POST /api/v1/orgs/{org}/projects/{project}/emails/deliveries/{id}/redeliver — re-queues a delivered or failed delivery, resetting its attempt history; pending and sending deliveries return a 409.

The same surface is in the SPA under project settings → “Email deliveries” (state filter, last error, redeliver). Delivery retries are tuned with EMAIL_MAX_ATTEMPTS (default 5), EMAIL_RETRY_BACKOFF_SECONDS (default 10, exponential) and EMAIL_POLL_SECONDS (default 10, how often the outbox is polled).

Configuration reference

Key	Default	Description
`EMAIL_SENDER`	`off`	`off`, `log`, `smtp`, `sendgrid`, `scaleway` or `http`.
`EMAIL_FROM`	–	Envelope and header From address.
`EMAIL_REPLY_TO`	–	Optional Reply-To address.
`EMAIL_BASE_URL`	–	Public web UI URL for links in emails.
`EMAIL_TIMEOUT_SECONDS`	`10`	Timeout per delivery attempt.
`EMAIL_MAX_ATTEMPTS`	`5`	Total delivery attempts per message.
`EMAIL_RETRY_BACKOFF_SECONDS`	`10`	Delay before the second attempt (exponential after).
`EMAIL_POLL_SECONDS`	`10`	How often the outbox is polled for due deliveries.
`EMAIL_SMTP_HOST`	–	SMTP host.
`EMAIL_SMTP_PORT`	per TLS mode	587 / 465 / 25 for starttls / ssl / none.
`EMAIL_SMTP_USERNAME`	–	SMTP username; empty skips authentication.
`EMAIL_SMTP_PASSWORD`	–	SMTP password.
`EMAIL_SMTP_TLS`	`starttls`	`starttls`, `ssl` or `none`.
`EMAIL_SMTP_INSECURE_SKIP_VERIFY`	`false`	Accept self-signed SMTP certificates.
`EMAIL_SENDGRID_API_KEY`	–	SendGrid API key.
`EMAIL_SENDGRID_ENDPOINT`	`https://api.sendgrid.com`	API base URL override.
`EMAIL_SCALEWAY_API_KEY`	–	Scaleway secret key.
`EMAIL_SCALEWAY_PROJECT_ID`	–	Scaleway project owning the verified domain.
`EMAIL_SCALEWAY_REGION`	`fr-par`	Scaleway region.
`EMAIL_SCALEWAY_ENDPOINT`	`https://api.scaleway.com`	API base URL override.
`EMAIL_HTTP_ENDPOINT`	–	Generic sender endpoint URL.
`EMAIL_HTTP_METHOD`	`POST`	HTTP method.
`EMAIL_HTTP_HEADERS`	–	JSON object of extra headers.
`EMAIL_HTTP_CONTENT_TYPE`	`application/json`	Request content type.
`EMAIL_HTTP_BODY_TEMPLATE`	provider-neutral JSON	Go text/template for the request body.

Email notifications