Better mail notification defaults.

law.cfg.example

@@ -986,13 +986,13 @@
 
 ; mail_smtp_host
 ; Description: The SMTP host for notifications sent by "law.notification.notify_mail".
-; Type: ``str``
-; Default: ``"127.0.0.1"``
+; Type: ``str``, ``None``
+; Default: ``None``
 
 ; mail_smtp_port
 ; Description: The SMTP port for notifications sent by "law.notification.notify_mail".
-; Type: ``int``
-; Default: ``25``
+; Type: ``int``, ``None``
+; Default: ``None``
 
 
 ; --- Options of contrib packages

law/config.py

@@ -138,8 +138,8 @@ def __str__(self) -> str:
         "notifications": {
             "mail_recipient": None,
             "mail_sender": None,
-            "mail_smtp_host": "127.0.0.1",
-            "mail_smtp_port": 25,
+            "mail_smtp_host": None,
+            "mail_smtp_port": None,
         },
         "bash_sandbox": {
             "stagein_dir_name": "stagein",

law/notification.py

@@ -33,21 +33,26 @@ def notify_mail(
     """
     cfg = Config.instance()
 
+    # get config recipient and sender values from config
     if not recipient:
         recipient = cfg.get_expanded("notifications", "mail_recipient")
     if not sender:
         sender = cfg.get_expanded("notifications", "mail_sender")
-    if not smtp_host:
-        smtp_host = cfg.get_expanded("notifications", "mail_smtp_host")
-    if not smtp_port:
-        smtp_port = cfg.get_expanded("notifications", "mail_smtp_port")
-
     if not recipient or not sender:
         logger.warning(
             f"cannot send mail notification, recipient ({recipient}) or sender ({sender}) empty",
         )
         return False
 
+    # get host and port
+    if not smtp_port:
+        smtp_port = cfg.get_expanded("notifications", "mail_smtp_port")
+    if not smtp_host:
+        smtp_host = cfg.get_expanded("notifications", "mail_smtp_host")
+    # infer host from sender when not set
+    if not smtp_host:
+        smtp_host = sender.split("@", 1)[1]
+
     mail_kwargs: dict[str, str | int] = {}
     if smtp_host:
         mail_kwargs["smtp_host"] = smtp_host

law/util.py

@@ -2124,7 +2124,7 @@ def send_mail(
     try:
         server = smtplib.SMTP(smtp_host, smtp_port)
     except Exception as e:
-        logger.warning(f"cannot create SMTP server: {e}")
+        logger.warning(f"cannot create SMTP server {smtp_host}:{smtp_port}: {e}")
         return False
 
     header = f"From: {sender}\r\nTo: {recipient}\r\nSubject: {subject}\r\n\r\n"