diff --git a/data/conf/dovecot/auth/mailcowauth.php b/data/conf/dovecot/auth/mailcowauth.php
index 667419c57..c625522ba 100644
--- a/data/conf/dovecot/auth/mailcowauth.php
+++ b/data/conf/dovecot/auth/mailcowauth.php
@@ -79,7 +79,9 @@ if ($isSOGoRequest) {
   }
 }
 if ($result === false){
-  $result = apppass_login($post['username'], $post['password'], array($post['service'] => true), array(
+  // If it's a SOGo Request, don't check for protocol access
+  $service = ($isSOGoRequest) ? false : array($post['service'] => true);
+  $result = apppass_login($post['username'], $post['password'], $service, array(
     'is_internal' => true,
     'remote_addr' => $post['real_rip']
   ));
diff --git a/data/conf/dovecot/auth/passwd-verify.lua b/data/conf/dovecot/auth/passwd-verify.lua
index 18c18dbe3..ea847932d 100644
--- a/data/conf/dovecot/auth/passwd-verify.lua
+++ b/data/conf/dovecot/auth/passwd-verify.lua
@@ -29,13 +29,23 @@ function auth_password_verify(request, password)
     insecure = true
   }
 
-  if c ~= 200 then
+  -- Returning PASSDB_RESULT_PASSWORD_MISMATCH will reset the user's auth cache entry.
+  -- Returning PASSDB_RESULT_INTERNAL_FAILURE keeps the existing cache entry,
+  -- even if the TTL has expired. Useful to avoid cache eviction during backend issues.
+  if c ~= 200 and c ~= 401 then
     dovecot.i_info("HTTP request failed with " .. c .. " for user " .. request.user)
-    return dovecot.auth.PASSDB_RESULT_INTERNAL_FAILURE, "Upstream error"
+    return dovecot.auth.PASSDB_RESULT_PASSWORD_MISMATCH, "Upstream error"
   end
 
-  local api_response = json.decode(table.concat(res))
-  if api_response.success == true then
+  local response_str = table.concat(res)
+  local is_response_valid, response_json = pcall(json.decode, response_str)
+
+  if not is_response_valid then
+    dovecot.i_info("Invalid JSON received: " .. response_str)
+    return dovecot.auth.PASSDB_RESULT_PASSWORD_MISMATCH, "Invalid response format"
+  end
+
+  if response_json.success == true then
     return dovecot.auth.PASSDB_RESULT_OK, ""
   end