Added support for sending with relay hosts

README.md

@@ -70,6 +70,10 @@ env vars
 * **POSTMOOGLE_MAILBOXES_ACTIVATION** - activation flow for new mailboxes, [docs/mailboxes.md](docs/mailboxes.md)
 * **POSTMOOGLE_MAXSIZE** - max email size (including attachments) in megabytes
 * **POSTMOOGLE_ADMINS** - a space-separated list of admin users. See `POSTMOOGLE_USERS` for syntax examples
+* **POSTMOOGLE_RELAY_HOST** - SMTP hostname of relay host (e.g. Sendgrid)
+* **POSTMOOGLE_RELAY_PORT** - SMTP port of relay host
+* **POSTMOOGLE_RELAY_USERNAME** - Username of relay host
+* **POSTMOOGLE_RELAY_PASSWORD** - Password of relay host
 
 You can find default values in [config/defaults.go](config/defaults.go)
 

cmd/cmd.go

@@ -143,6 +143,12 @@ func initSMTP(cfg *config.Config) {
 		MaxSize:     cfg.MaxSize,
 		Bot:         mxb,
 		Callers:     []smtp.Caller{mxb, q},
+		Relay: smtp.RelayConfig{
+			Host:     cfg.Relay.Host,
+			Port:     cfg.Relay.Port,
+			Usename:  cfg.Relay.Username,
+			Password: cfg.Relay.Password,
+		},
 	})
 }
 

config/config.go

@@ -46,6 +46,12 @@ func New() *Config {
 			DSN:     env.String("db.dsn", defaultConfig.DB.DSN),
 			Dialect: env.String("db.dialect", defaultConfig.DB.Dialect),
 		},
+		Relay: Relay{
+			Host:     env.String("relay.host", defaultConfig.Relay.Host),
+			Port:     env.String("relay.port", defaultConfig.Relay.Port),
+			Username: env.String("relay.username", defaultConfig.Relay.Username),
+			Password: env.String("relay.password", defaultConfig.Relay.Password),
+		},
 	}
 
 	return cfg

config/types.go

@@ -41,6 +41,8 @@ type Config struct {
 
 	// Monitoring config
 	Monitoring Monitoring
+
+	Relay Relay
 }
 
 // DB config
@@ -72,3 +74,11 @@ type Mailboxes struct {
 	Reserved   []string
 	Activation string
 }
+
+// Relay config
+type Relay struct {
+	Host     string
+	Port     string
+	Username string
+	Password string
+}

smtp/client.go

@@ -0,0 +1,107 @@
+package smtp
+
+import (
+	"crypto/tls"
+	"io"
+	"net/smtp"
+	"strings"
+
+	"gitlab.com/etke.cc/go/logger"
+	"gitlab.com/etke.cc/go/trysmtp"
+)
+
+type MailSender interface {
+	Send(from string, to string, data string) error
+}
+
+type Client struct {
+	config *RelayConfig
+	log    *logger.Logger
+}
+
+func newClient(cfg *RelayConfig, log *logger.Logger) Client {
+	return Client{
+		config: cfg,
+		log:    log,
+	}
+}
+
+func (c Client) Send(from string, to string, data string) error {
+	c.log.Debug("Sending email from %s to %s", from, to)
+	conn, err := c.createSmtpClient(from, to)
+	if conn == nil {
+		c.log.Error("cannot connect to SMTP server of %s: %v", to, err)
+		return err
+	}
+	if err != nil {
+		c.log.Warn("connection to the SMTP server of %s returned the following non-fatal error(-s): %v", err)
+	}
+	defer conn.Close()
+
+	var w io.WriteCloser
+	w, err = conn.Data()
+	if err != nil {
+		c.log.Error("cannot send DATA command: %v", err)
+		return err
+	}
+	defer w.Close()
+	c.log.Debug("sending DATA:\n%s", data)
+	_, err = strings.NewReader(data).WriteTo(w)
+	if err != nil {
+		c.log.Debug("cannot write DATA: %v", err)
+		return err
+	}
+
+	c.log.Debug("email has been sent")
+	return nil
+}
+
+func (c *Client) createSmtpClient(from string, to string) (*smtp.Client, error) {
+	if c.config.Host != "" {
+		return c.createDirectClient(from, to)
+	}
+
+	return trysmtp.Connect(from, to)
+}
+
+func (c *Client) createDirectClient(from string, to string) (*smtp.Client, error) {
+	localname := strings.SplitN(from, "@", 2)[1]
+	target := c.config.Host + ":" + c.config.Port
+	conn, err := smtp.Dial(target)
+
+	if err != nil {
+		return nil, err
+	}
+
+	err = conn.Hello(localname)
+	if err != nil {
+		return nil, err
+	}
+
+	if ok, _ := conn.Extension("STARTTLS"); ok {
+		config := &tls.Config{ServerName: c.config.Host}
+		conn.StartTLS(config) //nolint:errcheck // if it doesn't work - we can't do anything anyway
+	}
+
+	if c.config.Usename != "" {
+		err = conn.Auth(smtp.PlainAuth("", c.config.Usename, c.config.Password, c.config.Host))
+		if err != nil {
+			conn.Close()
+			return nil, err
+		}
+	}
+
+	err = conn.Mail(from)
+	if err != nil {
+		conn.Close()
+		return nil, err
+	}
+
+	err = conn.Rcpt(to)
+	if err != nil {
+		conn.Close()
+		return nil, err
+	}
+
+	return conn, nil
+}

smtp/manager.go

@@ -29,6 +29,7 @@ type Config struct {
 	MaxSize  int
 	Bot      matrixbot
 	Callers  []Caller
+	Relay    RelayConfig
 }
 
 type TLSConfig struct {
@@ -40,6 +41,13 @@ type TLSConfig struct {
 	Mu       sync.Mutex
 }
 
+type RelayConfig struct {
+	Host     string
+	Port     string
+	Usename  string
+	Password string
+}
+
 type Manager struct {
 	log  *logger.Logger
 	bot  matrixbot
@@ -71,10 +79,14 @@ type Caller interface {
 // NewManager creates new SMTP server manager
 func NewManager(cfg *Config) *Manager {
 	log := logger.New("smtp.", cfg.LogLevel)
+
+	smtpClient := newClient(&cfg.Relay, log)
+
 	mailsrv := &mailServer{
-		log:     log,
-		bot:     cfg.Bot,
-		domains: cfg.Domains,
+		log:        log,
+		bot:        cfg.Bot,
+		domains:    cfg.Domains,
+		mailSender: smtpClient,
 	}
 	for _, caller := range cfg.Callers {
 		caller.SetSendmail(mailsrv.SendEmail)

smtp/server.go

@@ -2,13 +2,10 @@ package smtp
 
 import (
 	"context"
-	"io"
-	"strings"
 
 	"github.com/emersion/go-smtp"
 	"github.com/getsentry/sentry-go"
 	"gitlab.com/etke.cc/go/logger"
-	"gitlab.com/etke.cc/go/trysmtp"
 
 	"gitlab.com/etke.cc/postmoogle/email"
 )
@@ -29,9 +26,10 @@ var (
 )
 
 type mailServer struct {
-	bot     matrixbot
-	log     *logger.Logger
-	domains []string
+	bot        matrixbot
+	log        *logger.Logger
+	domains    []string
+	mailSender MailSender
 }
 
 // Login used for outgoing mail submissions only (when you use postmoogle as smtp server in your scripts)
@@ -91,33 +89,7 @@ func (m *mailServer) AnonymousLogin(state *smtp.ConnectionState) (smtp.Session,
 
 // SendEmail to external mail server
 func (m *mailServer) SendEmail(from, to, data string) error {
-	m.log.Debug("Sending email from %s to %s", from, to)
-	conn, err := trysmtp.Connect(from, to)
-	if conn == nil {
-		m.log.Error("cannot connect to SMTP server of %s: %v", to, err)
-		return err
-	}
-	if err != nil {
-		m.log.Warn("connection to the SMTP server of %s returned the following non-fatal error(-s): %v", err)
-	}
-	defer conn.Close()
-
-	var w io.WriteCloser
-	w, err = conn.Data()
-	if err != nil {
-		m.log.Error("cannot send DATA command: %v", err)
-		return err
-	}
-	defer w.Close()
-	m.log.Debug("sending DATA:\n%s", data)
-	_, err = strings.NewReader(data).WriteTo(w)
-	if err != nil {
-		m.log.Debug("cannot write DATA: %v", err)
-		return err
-	}
-
-	m.log.Debug("email has been sent")
-	return nil
+	return m.mailSender.Send(from, to, data)
 }
 
 // ReceiveEmail - incoming mail into matrix room