Allow empty username

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

@@ -593,6 +593,9 @@ public class EmailService implements AutoCloseable {
         //System.setProperty("mail.socket.debug", Boolean.toString(debug));
         isession.addProvider(new GmailSSLProvider());
 
+        if (TextUtils.isEmpty(user))
+            user = null;
+
         if ("pop3".equals(protocol) || "pop3s".equals(protocol)) {
             iservice = isession.getStore(protocol);
             iservice.connect(address.getHostAddress(), port, user, null);

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

@@ -649,7 +649,7 @@ public class FragmentAccount extends FragmentBase {
                     throw new IllegalArgumentException(context.getString(R.string.title_no_host));
                 if (TextUtils.isEmpty(port))
                     port = (encryption == EmailService.ENCRYPTION_SSL ? "993" : "143");
-                if (TextUtils.isEmpty(user))
+                if (TextUtils.isEmpty(user) && !insecure)
                     throw new IllegalArgumentException(context.getString(R.string.title_no_user));
                 if (TextUtils.isEmpty(password) && !insecure && certificate == null)
                     throw new IllegalArgumentException(context.getString(R.string.title_no_password));
@@ -899,7 +899,7 @@ public class FragmentAccount extends FragmentBase {
                     throw new IllegalArgumentException(context.getString(R.string.title_no_host));
                 if (TextUtils.isEmpty(port))
                     port = (encryption == EmailService.ENCRYPTION_SSL ? "993" : "143");
-                if (TextUtils.isEmpty(user) && !should)
+                if (TextUtils.isEmpty(user) && !insecure && !should)
                     throw new IllegalArgumentException(context.getString(R.string.title_no_user));
                 if (synchronize && TextUtils.isEmpty(password) && !insecure && certificate == null && !should)
                     throw new IllegalArgumentException(context.getString(R.string.title_no_password));

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

@@ -721,7 +721,7 @@ public class FragmentIdentity extends FragmentBase {
                         port = "25";
                     else
                         port = "465";
-                if (TextUtils.isEmpty(user) && !should)
+                if (TextUtils.isEmpty(user) && !insecure && !should)
                     throw new IllegalArgumentException(context.getString(R.string.title_no_user));
                 if (synchronize && TextUtils.isEmpty(password) && !insecure && certificate == null && !should)
                     throw new IllegalArgumentException(context.getString(R.string.title_no_password));

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

@@ -365,7 +365,7 @@ public class FragmentPop extends FragmentBase {
                     throw new IllegalArgumentException(context.getString(R.string.title_no_host));
                 if (TextUtils.isEmpty(port))
                     port = (encryption == EmailService.ENCRYPTION_SSL ? "995" : "110");
-                if (TextUtils.isEmpty(user) && !should)
+                if (TextUtils.isEmpty(user) && !insecure && !should)
                     throw new IllegalArgumentException(context.getString(R.string.title_no_user));
                 if (synchronize && TextUtils.isEmpty(password) && !insecure && !should)
                     throw new IllegalArgumentException(context.getString(R.string.title_no_password));