Check mail.domain.tld as alternative host

app/src/main/java/eu/faircode/email/EmailProvider.java

@@ -35,6 +35,9 @@ import org.xmlpull.v1.XmlPullParserFactory;
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.net.HttpURLConnection;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.Socket;
 import java.net.URL;
 import java.net.UnknownHostException;
 import java.text.Collator;
@@ -70,6 +73,18 @@ public class EmailProvider {
         this.name = name;
     }
 
+    private EmailProvider(String name, String domain, String imap_prefix, String smtp_prefix) {
+        this.name = name;
+
+        this.imap_host = imap_prefix + "." + domain;
+        this.imap_port = 993;
+        this.imap_starttls = false;
+
+        this.smtp_host = smtp_prefix + "." + domain;
+        this.smtp_port = 587;
+        this.smtp_starttls = true;
+    }
+
     static List<EmailProvider> loadProfiles(Context context) {
         List<EmailProvider> result = null;
         try {
@@ -138,8 +153,13 @@ public class EmailProvider {
                 return addSpecials(context, fromDNS(domain));
             } catch (UnknownHostException ex1) {
                 Log.w(ex1);
-                Log.i("Provider from template domain=" + domain);
-                return addSpecials(context, fromTemplate(domain));
+                try {
+                    Log.i("Provider from template domain=" + domain);
+                    return addSpecials(context, fromTemplate(domain));
+                } catch (UnknownHostException ex2) {
+                    Log.w(ex2);
+                    throw new UnknownHostException(context.getString(R.string.title_setup_no_settings, domain));
+                }
             }
         }
     }
@@ -339,17 +359,34 @@ public class EmailProvider {
         return provider;
     }
 
-    private static EmailProvider fromTemplate(String domain) {
-        EmailProvider provider = new EmailProvider(domain);
-        provider.imap_host = "imap." + domain;
-        provider.imap_port = 993;
-        provider.imap_starttls = false;
+    private static EmailProvider fromTemplate(String domain) throws UnknownHostException {
+        if (checkTemplate(domain, "imap", 993, "smtp", 587))
+            return new EmailProvider(domain, domain, "imap", "smtp");
 
-        provider.smtp_host = "smtp." + domain;
-        provider.smtp_port = 587;
-        provider.smtp_starttls = true;
+        else if (checkTemplate(domain, "mail", 993, "mail", 587))
+            return new EmailProvider(domain, domain, "mail", "mail");
 
-        return provider;
+        else
+            throw new UnknownHostException();
+    }
+
+    private static boolean checkTemplate(
+            String domain, String imap_prefix, int imap_port, String smtp_prefix, int smtp_port) {
+        return isHostReachable(imap_prefix + "." + domain, imap_port, 5000) &&
+                isHostReachable(smtp_prefix + "." + domain, smtp_port, 5000);
+    }
+
+    static boolean isHostReachable(String host, int port, int timeoutms) {
+        Log.i("Checking " + host + ":" + port);
+        try (Socket socket = new Socket()) {
+            InetAddress iaddr = InetAddress.getByName(host);
+            InetSocketAddress inetSocketAddress = new InetSocketAddress(iaddr, port);
+            socket.connect(inetSocketAddress, timeoutms);
+            return true;
+        } catch (IOException ex) {
+            Log.w(ex);
+            return false;
+        }
     }
 
     private static void addDocumentation(EmailProvider provider, String href, String title) {

app/src/main/java/eu/faircode/email/FragmentQuickSetup.java

@@ -61,6 +61,7 @@ import com.sun.mail.imap.IMAPFolder;
 import com.sun.mail.imap.IMAPStore;
 
 import java.io.IOException;
+import java.net.UnknownHostException;
 import java.util.ArrayList;
 import java.util.Date;
 import java.util.List;
@@ -439,7 +440,7 @@ public class FragmentQuickSetup extends FragmentBase {
                     tvInstructions.setVisibility(View.VISIBLE);
                 }
 
-                if (ex instanceof IllegalArgumentException)
+                if (ex instanceof IllegalArgumentException || ex instanceof UnknownHostException)
                     Snackbar.make(view, ex.getMessage(), Snackbar.LENGTH_LONG).show();
                 else {
                     tvError.setText(Helper.formatThrowable(ex));

app/src/main/res/values/strings.xml

@@ -106,7 +106,7 @@
     <string name="title_setup_go">Go</string>
     <string name="title_setup_setting_gmail">Enable access for "less secure" apps</string>
     <string name="title_setup_setting_yahoo">Enable access for "less secure" apps</string>
-    <string name="title_setup_no_settings">No settings found for \'%1$s\'</string>
+    <string name="title_setup_no_settings">No settings found for domain \'%1$s\'</string>
     <string name="title_setup_quick_success">An account and an identity have successfully been added</string>
     <string name="title_setup_quick_failed">You can try to configure an account and an identity below too</string>
     <string name="title_setup_manage">Manage</string>