diff --git a/modoboa/webmail/lib/imaputils.py b/modoboa/webmail/lib/imaputils.py
index cfc9adbd6..d8eff0014 100644
--- a/modoboa/webmail/lib/imaputils.py
+++ b/modoboa/webmail/lib/imaputils.py
@@ -292,16 +292,21 @@ class IMAPconnector:
             return f"OR {old} {c}"
 
         if criterion == "both":
-            criterion = "from_addr, subject"
-        criterions = ""
-        for c in criterion.split(","):
-            if c == "from_addr":
-                key = "FROM"
-            elif c == "subject":
-                key = "SUBJECT"
-            else:
-                continue
-            criterions = or_criterion(criterions, f'({key} "{pattern}")')
+            criterion = "from_addr,subject"
+
+        if not pattern:
+            criterions = "ALL"
+        else:
+            criterions = ""
+            for c in criterion.split(","):
+                if c == "from_addr":
+                    key = "FROM"
+                elif c == "subject":
+                    key = "SUBJECT"
+                else:
+                    continue
+                criterions = or_criterion(criterions, f'({key} "{pattern}")')
+
         self.criterions = [bytearray(criterions, "utf8")]
 
     def messages_count(self, **kwargs) -> int:
diff --git a/modoboa/webmail/tests/test_lib_imaputils.py b/modoboa/webmail/tests/test_lib_imaputils.py
new file mode 100644
index 000000000..a16f6231d
--- /dev/null
+++ b/modoboa/webmail/tests/test_lib_imaputils.py
@@ -0,0 +1,33 @@
+"""mailutils tests"""
+
+import unittest
+
+from modoboa.webmail.lib.imaputils import IMAPconnector
+
+
+class ImapUtilsTestCase(unittest.TestCase):
+    """Test mail utils library"""
+
+    def setUp(self):
+        self.imap_connector = IMAPconnector(user="test", password="test")
+
+    def test_criterions_one_criterion_with_pattern(self):
+        """Test with Criterion and pattern"""
+        self.imap_connector.criterions = []
+        self.imap_connector.parse_search_parameters("from_addr", "bob")
+        result = [bytearray('(FROM "bob")', "utf8")]
+        self.assertEqual(self.imap_connector.criterions, result)
+
+    def test_criterions_both_criterion_with_pattern(self):
+        """Test with both Criterion and pattern"""
+        self.imap_connector.criterions = []
+        self.imap_connector.parse_search_parameters("both", "bob")
+        result = [bytearray('OR (FROM "bob") (SUBJECT "bob")', "utf8")]
+        self.assertEqual(self.imap_connector.criterions, result)
+
+    def test_criterions_one_criterion_without_pattern(self):
+        """Test with Criterion and empty pattern"""
+        self.imap_connector.criterions = []
+        self.imap_connector.parse_search_parameters("SEEN", "")
+        result = [bytearray("ALL", "utf8")]
+        self.assertEqual(self.imap_connector.criterions, result)