[Rspamd] Do not increment rate limit for emails from user to himself (#6706)

* [Rspamd] Do not increment rate limit for emails from user to himself

* Lowercase username and recipient address for comparison

Normalize username and recipient address comparison to lowercase.

data/conf/rspamd/lua/rspamd.local.lua

@@ -454,12 +454,18 @@ rspamd_config:register_symbol({
     local redis_params = rspamd_parse_redis_server('dyn_rl')
     local rspamd_logger = require "rspamd_logger"
     local envfrom = task:get_from(1)
+    local envrcpt = task:get_recipients(1) or {}
     local uname = task:get_user()
     if not envfrom or not uname then
       return false
     end
+
     local uname = uname:lower()
 
+    if #envrcpt == 1 and envrcpt[1].addr:lower() == uname then
+      return false
+    end
+
     local env_from_domain = envfrom[1].domain:lower() -- get smtp from domain in lower case
 
     local function redis_cb_user(err, data)