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mailsender/README.md
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Claude fb52ee2c27 Target JDK 25 LTS instead of JDK 27
maven.compiler.release and the enforcer floor go to 25, and both the
GitHub CI and the Gitea publish workflow use Temurin 25.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01G71TQ5jDETVwdUJxGAwaiT
2026-10-12 07:32:18 +00:00

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# mailsender
OpenPGP encryption for Spring Boot mail: discovers recipients' keys via Web Key Directory (WKD) and sends
PGP/MIME (RFC 3156), or hands mail to an encrypting relay. See [docs/PLAN.md](docs/PLAN.md) for the design
and milestone status.
Requires JDK 25 or newer; the Maven Wrapper (`./mvnw`) downloads Maven 3.9.11. Built on Spring Boot 4.1.1 and PGPainless 2.0.
```
./mvnw verify
```
## Modules
| Module | Contents |
|---|---|
| `mailsender-pgp-core` | WKD key discovery, caching, pinned keys, certificate validation, OpenPGP encryption, PGP/MIME (no Spring) |
| `mailsender-pgp-spring-boot-autoconfigure` | `mail.pgp.*` properties and beans |
| `mailsender-pgp-spring-boot-starter` | dependency bundle for applications |
| `mailsender-demo` | sample app that sends test mails |
## Installation
Releases and snapshots are published to the Gitea Maven registry of the `public` owner by
`.gitea/workflows/publish.yml` (push to `main` → `-SNAPSHOT`, tag `v1.2.3` → `1.2.3`):
```xml
<repositories>
<repository>
<id>gitea-public</id>
<url>https://YOUR-GITEA-HOST/api/packages/public/maven</url>
</repository>
</repositories>
<dependency>
<groupId>pro.thinhha.mailsender</groupId>
<artifactId>mailsender-pgp-spring-boot-starter</artifactId>
<version>0.1.0</version>
</dependency>
```
If the packages are not public, add a `<server>` with id `gitea-public` and a token with `read:package` scope to
your `settings.xml`.
## Usage
Add `pro.thinhha.mailsender:mailsender-pgp-spring-boot-starter`, configure `spring.mail.*` as usual, and send
through `SecureMailSender` instead of `JavaMailSender`:
```java
SendReport report = secureMailSender.send(message); // MimeMessage or SimpleMailMessage
```
Each recipient's key is looked up via WKD (cached) and validated. The message is then sent PGP/MIME-encrypted to
recipients with a usable key and in plaintext to the rest (logged as a downgrade), or refused with
`EncryptionPolicyException` if a `REQUIRE` recipient has no key. `SendReport` lists the outcome per recipient.
```yaml
mail:
pgp:
mode: BUILT_IN # or RELAY: hand plaintext to an encrypting gateway (mail.pgp.relay.*)
default-policy: OPPORTUNISTIC # REQUIRE | OPPORTUNISTIC | PLAINTEXT
mixed-mode: SPLIT # or FAIL
recipients:
"[*@partner.example]": REQUIRE
sender-keys: # your own PUBLIC key, so sent copies stay readable
"[noreply@example.com]": file:/etc/mail/noreply.pub.asc
```
Map keys that are addresses need the `[...]` brackets. See [docs/PLAN.md](docs/PLAN.md) for all options.
- `mail.pgp.protected-headers=true` encrypts the real Subject too (RFC 9788); the visible Subject becomes `[...]`.
- With Micrometer, `mail.pgp.recipients{outcome,policy,reason}`, `mail.pgp.refused`, `mail.pgp.key.lookup` and
`mail.pgp.key.cache.size` are recorded.
- With Actuator, expose `pgpkeys` to inspect an address (`GET /actuator/pgpkeys/{email}`) or evict cached keys
(`DELETE /actuator/pgpkeys/{email}`).
## Demo app
The demo app sends `DEMO_COUNT` test mails (default: 1 to `test@thinhha.pro`) through `SecureMailSender` and logs
the outcome per recipient: PGP/MIME-encrypted (RFC 3156) when a valid WKD key is found, otherwise plaintext.
Set `MAIL_PGP_MODE=RELAY` and `RELAY_HOST`/`RELAY_PORT`/`RELAY_USERNAME`/`RELAY_PASSWORD` to send via a gateway.
```
./mvnw -q install -DskipTests
SMTP_HOST=smtp.example.com SMTP_PORT=587 \
SMTP_USERNAME=me@example.com SMTP_PASSWORD='app-password' \
DEMO_TO=test@thinhha.pro DEMO_COUNT=1 \
java -jar mailsender-demo/target/mailsender-demo-0.1.0-SNAPSHOT.jar
```
| Variable | Default | Meaning |
|---|---|---|
| `SMTP_HOST` / `SMTP_PORT` | `localhost` / `587` | SMTP server |
| `SMTP_USERNAME` / `SMTP_PASSWORD` | empty | SMTP credentials |
| `SMTP_AUTH` / `SMTP_STARTTLS` | `true` / `true` | set to `false` for a local test server |
| `DEMO_TO` | `test@thinhha.pro` | recipient |
| `DEMO_FROM` | `SMTP_USERNAME` | sender address |
| `DEMO_COUNT` | `1` | number of mails |