android.content.ActivityNotFoundException: No Activity found to handle Intent

Hi friends,
I am trying to activate an activity from another activity using implicit intent.

Code fragment of mail activity:

Code (Text):

1. public void onClick(View view) {
2.         intent = new Intent(Intent.ACTION_SEND);
3.         int id = view.getId();
4.         switch (id) {
5.         case R.id.addButton: {
6.             date = reminderDate.getDayOfMonth();
7.             month = reminderDate.getMonth();
8.             year = reminderDate.getYear();
9.  
10.             hour = reminderTime.getCurrentHour();
11.             minute = reminderTime.getCurrentMinute();
12.  
13.             Log.d(TAG, String.format("%s, Date: %s/%s/%s, Time: %s:%s",
14.                     reminderText.getText().toString(), date, month, year, hour,
15.                     minute));
16.             intent.setType("plain/text");
17.             intent.putExtra("reminderText", reminderText.getText().toString());
18.             startActivity(intent);
19.             break;
20.  
21.         }
22.         case R.id.cancelButton: {
23.  
24.             Log.d(TAG, "Reminder Cancelled");
25.             Toast.makeText(this, "Reminder Cancelled", Toast.LENGTH_LONG)
26.                     .show();
27.             break;
28.  
29.         }
30.         }
31.     }

Androidmainfest.xml

Code (Text):

1. <?xml version="1.0" encoding="utf-8"?>
2. <manifest xmlns:android="http://schemas.android.com/apk/res/android"
3.     package="com.reminder"
4.     android:versionCode="1"
5.     android:versionName="1.0" >
6.  
7.     <uses-sdk android:minSdkVersion="10" />
8.  
9.     <application
10.         android:icon="@drawable/ic_launcher"
11.         android:label="@string/app_name" >
12.         <activity
13.             android:name=".QReminderActivity"
14.             android:label="@string/app_name" >
15.         </activity>
16.         <activity android:name=".TimerActivity" >
17.             <intent-filter>
18.                 <action android:name="android.intent.action.MAIN" />
19.  
20.                 <category android:name="android.intent.category.LAUNCHER" />
21.             </intent-filter>
22.         </activity>
23.         <activity android:name=".NotificationActivity" >
24.             <intent-filter>
25.                 <action android:name="android.intent.action.SEND" />
26.                 <data android:mimeType="plain/text"/>
27.             </intent-filter>
28.         </activity>
29.     </application>
30.  
31. </manifest>

Activity NotificationActivity is in proper place. But on clicking addButton I am getting following exception:

Can anyone please help me in finding the issue??

 

I added following line to AndroidManifest.xml and it worked

<category android:name="android.intent.category.DEFAULT"/>

I may have a working code but can anyone please explain me why this happened?