first commit

internal/accounts/provider_smtp_helper.go

@@ -0,0 +1,81 @@
+package accounts
+
+import (
+	"crypto/tls"
+	"encoding/json"
+	"fmt"
+	"net"
+	"net/smtp"
+	"strconv"
+
+	"gomail/internal/crypto"
+	"gomail/internal/db"
+)
+
+// sendViaSMTP delivers an outgoing message through a linked account's own
+// SMTP settings — stdlib net/smtp, same choice as internal/queue's
+// MXDeliverer, so outbound for both "GoMail relays for me" and "I'm using my
+// own IMAP+SMTP provider" stay on the same dependency-free foundation.
+func sendViaSMTP(account *db.LinkedAccount, mk *crypto.MasterKey, msg *OutgoingMessage) error {
+	plain, err := crypto.Decrypt(mk, account.ID, "linked-account-cred", account.CredentialEnc)
+	if err != nil {
+		return fmt.Errorf("decrypting stored credential: %w", err)
+	}
+	var cred IMAPCredential // same password shape reused for the paired SMTP auth
+	if err := json.Unmarshal(plain, &cred); err != nil {
+		return fmt.Errorf("parsing stored credential: %w", err)
+	}
+
+	addr := net.JoinHostPort(account.SMTPHost, strconv.Itoa(account.SMTPPort))
+	conn, err := net.DialTimeout("tcp", addr, dialTimeout)
+	if err != nil {
+		return fmt.Errorf("dial %s: %w", addr, err)
+	}
+	defer conn.Close()
+
+	if account.SMTPTLS == "implicit" {
+		// See provider_imap.go's connect() comment — same gap, same reason.
+		conn = tls.Client(conn, &tls.Config{ServerName: account.SMTPHost, InsecureSkipVerify: true})
+	}
+
+	client, err := smtp.NewClient(conn, account.SMTPHost)
+	if err != nil {
+		return fmt.Errorf("SMTP handshake: %w", err)
+	}
+	defer client.Close()
+
+	if account.SMTPTLS == "starttls" {
+		if ok, _ := client.Extension("STARTTLS"); ok {
+			if err := client.StartTLS(&tls.Config{ServerName: account.SMTPHost}); err != nil {
+				return fmt.Errorf("STARTTLS: %w", err)
+			}
+		}
+	}
+
+	auth := smtp.PlainAuth("", account.EmailAddress, cred.Password, account.SMTPHost)
+	if err := client.Auth(auth); err != nil {
+		return fmt.Errorf("SMTP auth: %w", err)
+	}
+
+	if err := client.Mail(account.EmailAddress); err != nil {
+		return err
+	}
+	for _, to := range msg.To {
+		if err := client.Rcpt(to); err != nil {
+			return err
+		}
+	}
+
+	w, err := client.Data()
+	if err != nil {
+		return err
+	}
+	raw := buildRFC5322(account.EmailAddress, msg)
+	if _, err := w.Write(raw); err != nil {
+		return err
+	}
+	if err := w.Close(); err != nil {
+		return err
+	}
+	return client.Quit()
+}