diff --git a/src/com/android/email/provider/AttachmentProvider.java b/src/com/android/email/provider/AttachmentProvider.java
index 8f85a57e1..f020d1627 100644
--- a/src/com/android/email/provider/AttachmentProvider.java
+++ b/src/com/android/email/provider/AttachmentProvider.java
@@ -196,31 +196,39 @@ public class AttachmentProvider extends ContentProvider {
      * @param mimeType The given mime type
      * @return A likely mime type for the attachment
      */
-    public static String inferMimeType(String fileName, String mimeType) {
-        if (fileName != null && fileName.toLowerCase().endsWith(".eml")) {
-            return "message/rfc822";
-        }
-        // If the given mime type appears to be non-empty and non-generic - return it
-        if (!TextUtils.isEmpty(mimeType) &&
-                !"application/octet-stream".equalsIgnoreCase(mimeType)) {
-            return mimeType;
-        }
+    public static String inferMimeType(final String fileName, final String mimeType) {
 
-        // Try to find an extension in the filename
-        if (!TextUtils.isEmpty(fileName)) {
-            String extension = getFilenameExtension(fileName);
-            if (!TextUtils.isEmpty(extension)) {
-                // Extension found.  Look up mime type, or synthesize if none found.
-                mimeType = MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension);
-                if (mimeType == null) {
-                    mimeType = "application/" + extension;
+        // NOTE mime-types are case-*sensitive* on Android.
+        // Return values from this method MUST always in lowercase.
+        String result = null;
+
+        if (fileName != null && fileName.toLowerCase().endsWith(".eml")) {
+            result = "message/rfc822";
+        } else {
+            // If the given mime type appears to be non-empty and non-generic - return it
+            if (!TextUtils.isEmpty(mimeType) &&
+                    !"application/octet-stream".equalsIgnoreCase(mimeType)) {
+                result = mimeType;
+            } else {
+                // Try to find an extension in the filename
+                if (!TextUtils.isEmpty(fileName)) {
+                    String extension = getFilenameExtension(fileName);
+                    if (!TextUtils.isEmpty(extension)) {
+                        // Extension found.  Look up mime type, or synthesize if none found.
+                        result = MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension);
+                        if (TextUtils.isEmpty(result)) {
+                            result = "application/" + extension;
+                        }
+                    }
                 }
-                return mimeType;
             }
         }
 
-        // Fallback case - no good guess could be made.
-        return "application/octet-stream";
+        if (TextUtils.isEmpty(result)) {
+            // Fallback case - no good guess could be made.
+            result = "application/octet-stream";
+        }
+        return result.toLowerCase();
     }
 
     /**
diff --git a/tests/src/com/android/email/provider/AttachmentProviderTests.java b/tests/src/com/android/email/provider/AttachmentProviderTests.java
index 5286be9ed..66cad9617 100644
--- a/tests/src/com/android/email/provider/AttachmentProviderTests.java
+++ b/tests/src/com/android/email/provider/AttachmentProviderTests.java
@@ -277,39 +277,42 @@ public class AttachmentProviderTests extends ProviderTestCase2<AttachmentProvide
      * If the filename has a recognizable extension and it converts to a mime type, return that.
      * If the filename has an unrecognized extension, return "application/extension"
      * Otherwise return "application/octet-stream".
+     *
+     * Also, all results should be in lowercase.
      */
     public void testInferMimeType() {
-        final String DEFAULT = "application/octet-stream";
-        final String FILE_PDF = "myfile.false.pdf";
-        final String FILE_ABC = "myfile.false.abc";
+        final String DEFAULT_MIX = "Application/Octet-stream";
+        final String DEFAULT_LOWER = DEFAULT_MIX.toLowerCase();
+        final String FILE_PDF = "myfile.false.pDf";
+        final String FILE_ABC = "myfile.false.aBc";
         final String FILE_NO_EXT = "myfile";
 
         // If the given mime type is non-empty and anything other than "application/octet-stream",
         // just return it.  (This is the most common case.)
-        assertEquals("mime/type", AttachmentProvider.inferMimeType(null, "mime/type"));
-        assertEquals("mime/type", AttachmentProvider.inferMimeType("", "mime/type"));
-        assertEquals("mime/type", AttachmentProvider.inferMimeType(FILE_PDF, "mime/type"));
+        assertEquals("mime/type", AttachmentProvider.inferMimeType(null, "Mime/TyPe"));
+        assertEquals("mime/type", AttachmentProvider.inferMimeType("", "Mime/TyPe"));
+        assertEquals("mime/type", AttachmentProvider.inferMimeType(FILE_PDF, "Mime/TyPe"));
 
         // If the filename has a recognizable extension and it converts to a mime type, return that.
         assertEquals("application/pdf", AttachmentProvider.inferMimeType(FILE_PDF, null));
         assertEquals("application/pdf", AttachmentProvider.inferMimeType(FILE_PDF, ""));
-        assertEquals("application/pdf", AttachmentProvider.inferMimeType(FILE_PDF, DEFAULT));
+        assertEquals("application/pdf", AttachmentProvider.inferMimeType(FILE_PDF, DEFAULT_MIX));
 
         // If the filename has an unrecognized extension, return "application/extension"
         assertEquals("application/abc", AttachmentProvider.inferMimeType(FILE_ABC, null));
         assertEquals("application/abc", AttachmentProvider.inferMimeType(FILE_ABC, ""));
-        assertEquals("application/abc", AttachmentProvider.inferMimeType(FILE_ABC, DEFAULT));
+        assertEquals("application/abc", AttachmentProvider.inferMimeType(FILE_ABC, DEFAULT_MIX));
 
         // Otherwise return "application/octet-stream".
-        assertEquals(DEFAULT, AttachmentProvider.inferMimeType(FILE_NO_EXT, null));
-        assertEquals(DEFAULT, AttachmentProvider.inferMimeType(FILE_NO_EXT, ""));
-        assertEquals(DEFAULT, AttachmentProvider.inferMimeType(FILE_NO_EXT, DEFAULT));
-        assertEquals(DEFAULT, AttachmentProvider.inferMimeType(null, null));
-        assertEquals(DEFAULT, AttachmentProvider.inferMimeType("", ""));
+        assertEquals(DEFAULT_LOWER, AttachmentProvider.inferMimeType(FILE_NO_EXT, null));
+        assertEquals(DEFAULT_LOWER, AttachmentProvider.inferMimeType(FILE_NO_EXT, ""));
+        assertEquals(DEFAULT_LOWER, AttachmentProvider.inferMimeType(FILE_NO_EXT, DEFAULT_MIX));
+        assertEquals(DEFAULT_LOWER, AttachmentProvider.inferMimeType(null, null));
+        assertEquals(DEFAULT_LOWER, AttachmentProvider.inferMimeType("", ""));
 
         // Test for eml files.
-        assertEquals("message/rfc822", AttachmentProvider.inferMimeType("a.eMl", "text/plain"));
-        assertEquals("message/rfc822", AttachmentProvider.inferMimeType("a.eml", DEFAULT));
+        assertEquals("message/rfc822", AttachmentProvider.inferMimeType("a.eMl", "Text/Plain"));
+        assertEquals("message/rfc822", AttachmentProvider.inferMimeType("a.eml", DEFAULT_MIX));
     }
 
     /**