diff --git a/packages/circuits/package.json b/packages/circuits/package.json
index 26a5729a..1280b4e7 100644
--- a/packages/circuits/package.json
+++ b/packages/circuits/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@zk-email/circuits",
-  "version": "6.3.0",
+  "version": "6.3.1",
   "license": "MIT",
   "scripts": {
     "publish": "yarn npm publish --access=public",
diff --git a/packages/contracts/UserOverrideableDKIMRegistry.sol b/packages/contracts/UserOverrideableDKIMRegistry.sol
index d7f8a331..a5fee5f3 100644
--- a/packages/contracts/UserOverrideableDKIMRegistry.sol
+++ b/packages/contracts/UserOverrideableDKIMRegistry.sol
@@ -43,6 +43,9 @@ contract UserOverrideableDKIMRegistry is
         address indexed authorizer
     );
 
+    /// @notice Emitted when the main authorizer address is changed.
+    event MainAuthorizerChanged(address indexed newMainAuthorizer);
+
     /// @notice Main authorizer address.
     address public mainAuthorizer;
 
@@ -356,6 +359,27 @@ contract UserOverrideableDKIMRegistry is
         emit DKIMPublicKeyHashReactivated(publicKeyHash, authorizer);
     }
 
+    /**
+     * @notice Changes the main authorizer address.
+     * @param newMainAuthorizer The address of the new main authorizer.
+     * @custom:require Only the owner can change the main authorizer address.
+     * @custom:require The new main authorizer address cannot be zero.
+     * @custom:require The new main authorizer address cannot be the same as the current main authorizer.
+     * @custom:event MainAuthorizerChanged Emitted when the main authorizer address changes.
+     */
+    function changeMainAuthorizer(address newMainAuthorizer) public onlyOwner {
+        require(
+            newMainAuthorizer != address(0),
+            "newMainAuthorizer address cannot be zero"
+        );
+        require(
+            newMainAuthorizer != mainAuthorizer,
+            "newMainAuthorizer address cannot be the same as the current mainAuthorizer"
+        );
+        mainAuthorizer = newMainAuthorizer;
+        emit MainAuthorizerChanged(newMainAuthorizer);
+    }
+
     /**
      * @notice Computes a signed message string for setting or revoking a DKIM public key hash.
      * @param prefix The operation prefix (SET: or REVOKE:).
diff --git a/packages/contracts/package.json b/packages/contracts/package.json
index 6b48d728..65ca80d0 100644
--- a/packages/contracts/package.json
+++ b/packages/contracts/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@zk-email/contracts",
-  "version": "6.3.0",
+  "version": "6.3.1",
   "license": "MIT",
   "scripts": {
     "build": "forge build",
diff --git a/packages/contracts/test/UserOverrideableDKIMRegistry.t.sol b/packages/contracts/test/UserOverrideableDKIMRegistry.t.sol
index c7b65619..8fdd5cbc 100644
--- a/packages/contracts/test/UserOverrideableDKIMRegistry.t.sol
+++ b/packages/contracts/test/UserOverrideableDKIMRegistry.t.sol
@@ -590,6 +590,22 @@ contract UserOverrideableDKIMRegistryTest is Test {
         vm.stopPrank();
     }
 
+    function testChangeMainAuthorizer() public {
+        vm.startPrank(deployer);
+        vm.expectEmit();
+        emit UserOverrideableDKIMRegistry.MainAuthorizerChanged(user1);
+        registry.changeMainAuthorizer(user1);
+        vm.stopPrank();
+    }
+
+    function testChangeMainAuthorizerContract() public {
+        vm.startPrank(deployer);
+        vm.expectEmit();
+        emit UserOverrideableDKIMRegistry.MainAuthorizerChanged(user1);
+        registryWithContract.changeMainAuthorizer(address(user1));
+        vm.stopPrank();
+    }
+
     function testFailIsDKIMPublicKeyHashValidByUser2() public {
         testSetDKIMPublicKeyHashByUser1();
 
@@ -1099,4 +1115,32 @@ contract UserOverrideableDKIMRegistryTest is Test {
         );
         console.log(signedMsg);
     }
+
+    function testExpectRevertChangeMainAuthorizerByNonOwner() public {
+        vm.startPrank(mainAuthorizer);
+        vm.expectRevert(
+            abi.encodeWithSelector(
+                OwnableUpgradeable.OwnableUnauthorizedAccount.selector,
+                mainAuthorizer
+            )
+        );
+        registry.changeMainAuthorizer(user1);
+        vm.stopPrank();
+    }
+
+    function testExpectRevertChangeMainAuthorizerIsZero() public {
+        vm.startPrank(deployer);
+        vm.expectRevert("newMainAuthorizer address cannot be zero");
+        registry.changeMainAuthorizer(address(0));
+        vm.stopPrank();
+    }
+
+    function testExpectRevertChangeMainAuthorizerIsSame() public {
+        vm.startPrank(deployer);
+        vm.expectRevert(
+            "newMainAuthorizer address cannot be the same as the current mainAuthorizer"
+        );
+        registry.changeMainAuthorizer(mainAuthorizer);
+        vm.stopPrank();
+    }
 }
diff --git a/packages/helpers/package.json b/packages/helpers/package.json
index 93a8909f..6a684c38 100644
--- a/packages/helpers/package.json
+++ b/packages/helpers/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@zk-email/helpers",
-  "version": "6.3.0",
+  "version": "6.3.1",
   "license": "MIT",
   "main": "dist",
   "scripts": {