diff --git a/src/java/davmail/util/StringUtil.java b/src/java/davmail/util/StringUtil.java
index 2a8f5453..9e6a4e4c 100644
--- a/src/java/davmail/util/StringUtil.java
+++ b/src/java/davmail/util/StringUtil.java
@@ -151,6 +151,7 @@ public final class StringUtil {
     private static final Pattern URLENCODED_HASH_PATTERN = Pattern.compile("%23");
     private static final Pattern URLENCODED_STAR_PATTERN = Pattern.compile("%2A");
     private static final Pattern URLENCODED_PIPE_PATTERN = Pattern.compile("%7C");
+    private static final Pattern URLENCODED_QUESTION_PATTERN = Pattern.compile("%3F");
 
     private static final Pattern ENCODED_AMP_PATTERN = Pattern.compile("&");
     private static final Pattern ENCODED_LT_PATTERN = Pattern.compile("<");
@@ -165,6 +166,7 @@ public final class StringUtil {
     private static final Pattern UNDERSCORE_PATTERN = Pattern.compile("_");
     private static final Pattern DASH_PATTERN = Pattern.compile("-");
     private static final Pattern PIPE_PATTERN = Pattern.compile("\\|");
+    private static final Pattern QUESTION_PATTERN = Pattern.compile("\\?");
 
     // WebDav search parameter encode
     private static final Pattern APOS_PATTERN = Pattern.compile("'");
@@ -334,6 +336,9 @@ public final class StringUtil {
         if (result.indexOf('|') >= 0) {
             result = PIPE_PATTERN.matcher(result).replaceAll("%7C");
         }
+        if (result.indexOf('?') >= 0) {
+            result = QUESTION_PATTERN.matcher(result).replaceAll("%3F");
+        }
         return result;
     }
 
@@ -380,6 +385,9 @@ public final class StringUtil {
             if (result.indexOf("%7C") >= 0) {
                 result = URLENCODED_PIPE_PATTERN.matcher(result).replaceAll("|");
             }
+            if (result.indexOf("%3F") >= 0) {
+                result = URLENCODED_QUESTION_PATTERN.matcher(result).replaceAll("?");
+            }
             // last replace %
             if (result.indexOf("%25") >= 0) {
                 result = URLENCODED_PERCENT_PATTERN.matcher(result).replaceAll("%");
diff --git a/src/test/davmail/util/StringUtilTest.java b/src/test/davmail/util/StringUtilTest.java
index 6d706488..7a7612af 100644
--- a/src/test/davmail/util/StringUtilTest.java
+++ b/src/test/davmail/util/StringUtilTest.java
@@ -19,6 +19,8 @@
 package davmail.util;
 
 import junit.framework.TestCase;
+import org.apache.commons.httpclient.URIException;
+import org.apache.commons.httpclient.util.URIUtil;
 
 /**
  * Test StringUtil.
@@ -107,4 +109,14 @@ public class StringUtilTest extends TestCase {
         assertEquals("test %7C", StringUtil.encodeUrlcompname("test |"));
         assertEquals("test |", StringUtil.decodeUrlcompname("test %7C"));
     }
+
+    public void testEncodeQuestion() {
+        try {
+            URIUtil.encodeWithinQuery("test ?");
+        } catch (URIException e) {
+            e.printStackTrace();
+        }
+        assertEquals("test %3F", StringUtil.encodeUrlcompname("test ?"));
+        assertEquals("test ?", StringUtil.decodeUrlcompname("test %3F"));
+    }
 }