Struct certificate checking by default

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

@@ -831,6 +831,11 @@ public class ApplicationEx extends Application
                 editor.putBoolean("updown", false);
         } else if (version < 2113)
             editor.remove("send_more");
+        else if (version < 2137) {
+            // https://support.google.com/faqs/answer/6346016
+            if (!prefs.contains("cert_strict"))
+                editor.putBoolean("cert_strict", !BuildConfig.PLAY_STORE_RELEASE);
+        }
 
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O && !BuildConfig.DEBUG)
             editor.remove("background_service");

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

@@ -189,7 +189,7 @@ public class EmailService implements AutoCloseable {
         this.log = prefs.getBoolean("protocol", false);
         this.ssl_harden = prefs.getBoolean("ssl_harden", false);
         this.ssl_harden_strict = prefs.getBoolean("ssl_harden_strict", false);
-        this.cert_strict = prefs.getBoolean("cert_strict", !BuildConfig.PLAY_STORE_RELEASE);
+        this.cert_strict = prefs.getBoolean("cert_strict", true);
 
         boolean auth_plain = prefs.getBoolean("auth_plain", true);
         boolean auth_login = prefs.getBoolean("auth_login", true);

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

@@ -658,7 +658,7 @@ public class FragmentOptionsConnection extends FragmentBase implements SharedPre
             swSslHarden.setChecked(prefs.getBoolean("ssl_harden", false));
             swSslHardenStrict.setChecked(prefs.getBoolean("ssl_harden_strict", false));
             swSslHardenStrict.setEnabled(swSslHarden.isChecked());
-            swCertStrict.setChecked(prefs.getBoolean("cert_strict", !BuildConfig.PLAY_STORE_RELEASE));
+            swCertStrict.setChecked(prefs.getBoolean("cert_strict", true));
             swOpenSafe.setChecked(prefs.getBoolean("open_safe", false));
             swBouncyCastle.setChecked(prefs.getBoolean("bouncy_castle", false));
             swFipsMode.setChecked(prefs.getBoolean("bc_fips", false));

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

@@ -2923,7 +2923,7 @@ public class Log {
                 boolean tcp_keep_alive = prefs.getBoolean("tcp_keep_alive", false);
                 boolean ssl_harden = prefs.getBoolean("ssl_harden", false);
                 boolean ssl_harden_strict = (ssl_harden && prefs.getBoolean("ssl_harden_strict", false));
-                boolean cert_strict = prefs.getBoolean("cert_strict", !BuildConfig.PLAY_STORE_RELEASE);
+                boolean cert_strict = prefs.getBoolean("cert_strict", true);
                 boolean open_safe = prefs.getBoolean("open_safe", false);
 
                 size += write(os, "timeout=" + timeout + "s" + (timeout == EmailService.DEFAULT_CONNECT_TIMEOUT ? "" : " !!!") + "\r\n");