first commit

backend/app/services/mail_sender.py

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+import email.policy
+import email.utils
+from email.message import EmailMessage
+
+import aiosmtplib
+import dkim
+
+from app.config import get_settings
+from app.models import MailDomain
+
+SMTP_POLICY = email.policy.SMTP.clone(max_line_length=998)
+
+
+def build_message(
+    *,
+    sender: str,
+    recipients: list[str],
+    cc: list[str],
+    subject: str,
+    body_text: str,
+    body_html: str | None,
+) -> EmailMessage:
+    message = EmailMessage(policy=SMTP_POLICY)
+    message["From"] = sender
+    message["To"] = ", ".join(recipients)
+    if cc:
+        message["Cc"] = ", ".join(cc)
+    message["Subject"] = subject
+    message["Date"] = email.utils.formatdate(localtime=True)
+    message["Message-ID"] = email.utils.make_msgid(domain=sender.split("@")[-1])
+    message.set_content(body_text)
+    if body_html:
+        message.add_alternative(body_html, subtype="html")
+    return message
+
+
+def sign_message(message: EmailMessage, domain: MailDomain) -> bytes:
+    raw_message = message.as_bytes(policy=SMTP_POLICY)
+    signed_headers = [
+        b"from",
+        b"to",
+        b"subject",
+        b"date",
+        b"message-id",
+        b"mime-version",
+        b"content-type",
+    ]
+    if message.get("Cc"):
+        signed_headers.insert(3, b"cc")
+    signature = dkim.sign(
+        raw_message,
+        domain.dkim_selector.encode(),
+        domain.domain_name.encode(),
+        domain.dkim_private_key.encode(),
+        include_headers=signed_headers,
+        canonicalize=(b"relaxed", b"relaxed"),
+    )
+    if not signature.endswith(b"\r\n"):
+        signature += b"\r\n"
+    return signature + raw_message
+
+
+async def send_via_smtp(
+    message_bytes: bytes,
+    *,
+    sender: str,
+    recipients: list[str],
+) -> None:
+    settings = get_settings()
+    await aiosmtplib.send(
+        message_bytes,
+        sender=sender,
+        recipients=recipients,
+        hostname=settings.smtp_host,
+        port=settings.smtp_port,
+        username=settings.smtp_username or None,
+        password=settings.smtp_password or None,
+        start_tls=settings.smtp_use_tls,
+        timeout=settings.smtp_timeout,
+    )
+
+
+async def deliver_email(
+    *,
+    sender: str,
+    recipients: list[str],
+    cc: list[str],
+    bcc: list[str],
+    subject: str,
+    body_text: str,
+    body_html: str | None,
+    domain: MailDomain,
+) -> None:
+    message = build_message(
+        sender=sender,
+        recipients=recipients,
+        cc=cc,
+        subject=subject,
+        body_text=body_text,
+        body_html=body_html,
+    )
+    signed = sign_message(message, domain)
+    await send_via_smtp(
+        signed,
+        sender=sender,
+        recipients=[*recipients, *cc, *bcc],
+    )