fix: Date/Message-ID/From-name on ticket emails, richer body (1.6.1-aio.9)

A tester's ticket email landed in spam. A mail-tester run against demo
scored 8.3/10 with SPF, DKIM and DMARC all passing through the VPS relay,
so the deductions were all in the message: MISSING_DATE (1.4),
HTML_IMAGE_ONLY_04 (0.3), MISSING_MID (0.1) — and Gmail/Outlook weigh a
missing Date/Message-ID as "machine-generated" far more than that.

- `build_ticket_email` sets Date, a Message-ID under the sender domain,
  and a From display name from `lnbits_site_title`.
- The body now carries the event name, dates, location, name on ticket,
  ticket id and the door instruction, so the HTML part is no longer a
  QR with a handful of words.

Upstream candidate: lnbits core `send_email` has the same omissions.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EYwoAkZZmXMMmaBp4WGUBo

services.py

@@ -5,6 +5,7 @@ import smtplib
 from asyncio.tasks import create_task
 from email.mime.multipart import MIMEMultipart
 from email.mime.text import MIMEText
+from email.utils import formataddr, formatdate, make_msgid
 from html import escape
 
 from lnbits.core.models.users import UserNotifications
@@ -114,12 +115,34 @@ def _ticket_notification_message(ticket: Ticket, event: Event) -> tuple[str, str
     return subject, f"{body}\n\nOpen it here: {ticket_url}"
 
 
-def _ticket_delivery_message(ticket: Ticket, base_message: str) -> str:
-    return f"{base_message}\n\nTicket image: {_ticket_image_url(ticket)}"
+def _ticket_details(ticket: Ticket, event: Event) -> str:
+    """Human-readable ticket facts for the email body. Also what keeps the
+    mail from being an image with no words (SpamAssassin HTML_IMAGE_ONLY)."""
+    when = event.event_start_date
+    if event.event_end_date and event.event_end_date != event.event_start_date:
+        when = f"{when} to {event.event_end_date}"
+    lines = [f"Event: {event.name}", f"When: {when}"]
+    if event.location:
+        lines.append(f"Where: {event.location}")
+    if ticket.name:
+        lines.append(f"Name on ticket: {ticket.name}")
+    lines.append(f"Ticket ID: {ticket.id}")
+    lines.append(
+        "Show the QR code below (or open the link above on your phone) at the "
+        "door to be scanned in."
+    )
+    return "\n".join(lines)
 
 
-def _ticket_email_html_message(ticket: Ticket, base_message: str) -> str:
-    text_message = _ticket_delivery_message(ticket, base_message)
+def _ticket_delivery_message(ticket: Ticket, event: Event, base_message: str) -> str:
+    return (
+        f"{base_message}\n\n{_ticket_details(ticket, event)}"
+        f"\n\nTicket image: {_ticket_image_url(ticket)}"
+    )
+
+
+def _ticket_email_html_message(ticket: Ticket, event: Event, base_message: str) -> str:
+    text_message = _ticket_delivery_message(ticket, event, base_message)
     html_message = f"<p>{escape(text_message).replace(chr(10), '<br />')}</p>"
     image_url = escape(_ticket_image_url(ticket), quote=True)
     return (
@@ -131,8 +154,8 @@ def _ticket_email_html_message(ticket: Ticket, base_message: str) -> str:
 
 def _ticket_notification_payload(ticket: Ticket, event: Event) -> tuple[str, str, str]:
     subject, base_message = _ticket_notification_message(ticket, event)
-    text_message = _ticket_delivery_message(ticket, base_message)
-    html_message = _ticket_email_html_message(ticket, base_message)
+    text_message = _ticket_delivery_message(ticket, event, base_message)
+    html_message = _ticket_email_html_message(ticket, event, base_message)
     return subject, text_message, html_message
 
 
@@ -221,14 +244,7 @@ async def _send_ticket_email_notification(
         if not is_valid_email_address(address):
             raise ValueError(f"Invalid email address: {address}")
 
-    msg = MIMEMultipart("alternative")
-    msg["From"] = from_email
-    msg["To"] = ", ".join(to_emails)
-    msg["Subject"] = subject
-    msg.attach(MIMEText(message, "plain"))
-    if html_message:
-        msg.attach(MIMEText(html_message, "html"))
-
+    msg = build_ticket_email(from_email, to_emails, subject, message, html_message)
     username = settings.lnbits_email_notifications_username or from_email
     await asyncio.to_thread(
         _smtp_send,
@@ -242,6 +258,31 @@ async def _send_ticket_email_notification(
     )
 
 
+def build_ticket_email(
+    from_email: str,
+    to_emails: list[str],
+    subject: str,
+    message: str,
+    html_message: str | None = None,
+) -> MIMEMultipart:
+    """Assemble the multipart ticket email with the headers receivers score
+    on: a Date and a Message-ID (their absence is what SpamAssassin's
+    MISSING_DATE / MISSING_MID flag, and what Gmail/Outlook read as
+    machine-generated), and a display name on From so the sender is not a
+    bare address."""
+    msg = MIMEMultipart("alternative")
+    sender_name = (settings.lnbits_site_title or "").strip() or "Tickets"
+    msg["From"] = formataddr((sender_name, from_email))
+    msg["To"] = ", ".join(to_emails)
+    msg["Subject"] = subject
+    msg["Date"] = formatdate(localtime=True)
+    msg["Message-ID"] = make_msgid(domain=from_email.rsplit("@", 1)[-1])
+    msg.attach(MIMEText(message, "plain"))
+    if html_message:
+        msg.attach(MIMEText(html_message, "html"))
+    return msg
+
+
 def _smtp_send(
     server: str,
     port: int,