FIX (email): Add login auth in case if plain fails

Author: RostislavDugin

backend/internal/features/notifiers/models/email_notifier/dto.go

@@ -0,0 +1,28 @@
+package email_notifier
+
+import (
+	"errors"
+	"net/smtp"
+)
+
+type loginAuth struct {
+	username, password string
+}
+
+func (a *loginAuth) Start(server *smtp.ServerInfo) (string, []byte, error) {
+	return "LOGIN", []byte{}, nil
+}
+
+func (a *loginAuth) Next(fromServer []byte, more bool) ([]byte, error) {
+	if more {
+		switch string(fromServer) {
+		case "Username:":
+			return []byte(a.username), nil
+		case "Password:":
+			return []byte(a.password), nil
+		default:
+			return nil, errors.New("unknown LOGIN challenge: " + string(fromServer))
+		}
+	}
+	return nil, nil
+}

backend/internal/features/notifiers/models/email_notifier/model.go

@@ -132,9 +132,8 @@ func (e *EmailNotifier) Send(
 
 		// Set up authentication only if credentials are provided
 		if isAuthRequired {
-			auth := smtp.PlainAuth("", e.SMTPUser, smtpPassword, e.SMTPHost)
-			if err := client.Auth(auth); err != nil {
-				return fmt.Errorf("SMTP authentication failed: %w", err)
+			if err := e.authenticate(client, smtpPassword); err != nil {
+				return err
 			}
 		}
 
@@ -195,9 +194,8 @@ func (e *EmailNotifier) Send(
 
 		// Authenticate only if credentials are provided
 		if isAuthRequired {
-			auth := smtp.PlainAuth("", e.SMTPUser, smtpPassword, e.SMTPHost)
-			if err := client.Auth(auth); err != nil {
-				return fmt.Errorf("SMTP authentication failed: %w", err)
+			if err := e.authenticate(client, smtpPassword); err != nil {
+				return err
 			}
 		}
 
@@ -256,3 +254,19 @@ func (e *EmailNotifier) EncryptSensitiveData(encryptor encryption.FieldEncryptor
 	}
 	return nil
 }
+
+func (e *EmailNotifier) authenticate(client *smtp.Client, password string) error {
+	// Try PLAIN auth first (most common)
+	plainAuth := smtp.PlainAuth("", e.SMTPUser, password, e.SMTPHost)
+	if err := client.Auth(plainAuth); err == nil {
+		return nil
+	}
+
+	// If PLAIN fails, try LOGIN auth (required by Office 365 and some providers)
+	loginAuth := &loginAuth{e.SMTPUser, password}
+	if err := client.Auth(loginAuth); err != nil {
+		return fmt.Errorf("SMTP authentication failed: %w", err)
+	}
+
+	return nil
+}