refactor MailProvider model and enhance email validation in admin form

api/admin.py

@@ -1,4 +1,6 @@
+import logging
 import smtplib
+import socket
 
 from django.contrib import admin
 from django import forms
@@ -6,6 +8,8 @@ from django.core.exceptions import ValidationError
 
 from api.models import MailProvider
 
+_logger = logging.getLogger(__name__)
+
 class MailProviderForm(forms.ModelForm):
     host_password = forms.CharField(widget=forms.PasswordInput(render_value=True))
 
@@ -21,11 +25,26 @@ class MailProviderForm(forms.ModelForm):
         password = cleaned_data.get("host_password")
         use_tls = cleaned_data.get("use_tls")
 
+        if host:
+            try:
+                socket.gethostbyname(host)
+            except socket.gaierror:
+                raise ValidationError(
+                    "Invalid mail server hostname. Could not resolve host."
+                )
+
         if host and port and user and password:
             try:
-                connection = smtplib.SMTP(host, port, timeout=10)
-                if use_tls:
-                    connection.starttls()
+                if port == 465:
+                    connection = smtplib.SMTP_SSL(host, port, timeout=10)
+                else:
+                    connection = smtplib.SMTP(host, port, timeout=10)
+                    if use_tls and port == 465:
+                        raise ValidationError(
+                            "Port 465 should not be used with STARTTLS. Use SMTP_SSL instead or change to port 587."
+                        )
+                    if use_tls:
+                        connection.starttls()
                 connection.login(user, password)
                 connection.quit()
             except Exception as e:

api/migrations/0002_alter_mailprovider_host.py

@@ -0,0 +1,18 @@
+# Generated by Django 5.2.1 on 2025-05-27 21:48
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('api', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='mailprovider',
+            name='host',
+            field=models.CharField(max_length=255),
+        ),
+    ]

api/models.py

@@ -1,7 +1,7 @@
 from django.db import models
 
 class MailProvider(models.Model):
-    host = models.URLField()
+    host = models.CharField(max_length=255)
     port = models.IntegerField(default=587)
     host_user = models.CharField(max_length=255)
     host_password = models.CharField(max_length=255)