diff --git a/functions.lua b/functions.lua
index 3cfbc60..fc35c47 100644
--- a/functions.lua
+++ b/functions.lua
@@ -228,7 +228,17 @@ function fediauth.give_code(secret_b32, time)
     return codeseq
 end
 
-function fediauth.str_repeats(s,c)
-    local _,n = s:gsub(c,"")
-    return n
+function fediauth.check_for_restricted_instance(domain)
+   local restricted_instances = minetest.settings:get("fediauth.restricted_instances") or {}
+   if type(restricted_instances) == "string" then
+	restricted_instances = restricted_instances:split(",")
+   end
+   for _, instance in ipairs(restricted_instances) do
+	if instance == domain then
+		minetest.log("action", "[fediauth] domain restricted: '" .. domain .. "'")
+		return true
+	end
+   end
+   return false
 end
+
diff --git a/join.lua b/join.lua
index 9ffe209..0ae0f63 100644
--- a/join.lua
+++ b/join.lua
@@ -124,11 +124,22 @@ minetest.register_on_player_receive_fields(function(player, formname, fields)
     -- check for new player or doesn't have fedi account
     if fields.fediverse_account_url then
 	-- basic prevent mention spam and limit length
-	if not string.starts(fields.fediverse_account_url, "@") or string.len(fields.fediverse_account_url) < 3 or string.len(fields.fediverse_account_url) > 100 or fediauth.str_repeats(fields.fediverse_account_url, "@") > 2 then
+	if not string.starts(fields.fediverse_account_url, "@") or string.len(fields.fediverse_account_url) < 3 or string.len(fields.fediverse_account_url) > 100 then
 		minetest.chat_send_player(playername, minetest.colorize("#ff0000", "Try again, your input is incorrect"))
 		minetest.show_formspec(playername, FORMNAMEFEDI, formspecfediadd)
 		return
 	end
+	fedihandle = fields.fediverse_account_url:split("@")
+	if #fedihandle ~= 2 then
+		minetest.chat_send_player(playername, minetest.colorize("#ff0000", "Incorrect format"))
+		minetest.show_formspec(playername, FORMNAMEFEDI, formspecfediadd)
+		return
+	end
+	if fediauth.check_for_restricted_instance(fedihandle[2]) then
+		minetest.chat_send_player(playername, minetest.colorize("#ff0000", fedihandle[2] .. "has restricted, try another..."))
+		minetest.show_formspec(playername, FORMNAMEFEDI, formspecfediadd)
+		return
+	end
         local secret_b32 = fediauth.get_player_secret_b32(playername)
         local codeseq = fediauth.give_code(secret_b32)
 	fediauth.send_code(codeseq[1], fields.fediverse_account_url)
diff --git a/onboard.lua b/onboard.lua
index d84ab1f..9f2f571 100644
--- a/onboard.lua
+++ b/onboard.lua
@@ -39,12 +39,22 @@ minetest.register_on_player_receive_fields(function(player, formname, fields)
         return
     end
 
-	if fields.fediverse_account_url then
+    if fields.fediverse_account_url then
         local playername = player:get_player_name()
-		if not string.starts(fields.fediverse_account_url, "@") or string.len(fields.fediverse_account_url) < 3 or string.len(fields.fediverse_account_url) > 100 then
-            		minetest.chat_send_player(playername, minetest.colorize("#ff0000", "Try again, your input is incorrect"))
-			return
-		end
+	-- basic prevent mention spam and limit length
+	if not string.starts(fields.fediverse_account_url, "@") or string.len(fields.fediverse_account_url) < 3 or string.len(fields.fediverse_account_url) > 100 then
+		minetest.chat_send_player(playername, minetest.colorize("#ff0000", "Try again, your input is incorrect"))
+		return
+	end
+	fedihandle = fields.fediverse_account_url:split("@")
+	if #fedihandle ~= 2 then
+		minetest.chat_send_player(playername, minetest.colorize("#ff0000", "Incorrect format"))
+		return
+	end
+	if fediauth.check_for_restricted_instance(fedihandle[2]) then
+		minetest.chat_send_player(playername, minetest.colorize("#ff0000", fedihandle[2] .. "has restricted, try another..."))
+		return
+	end
         local secret_b32 = fediauth.get_player_secret_b32(playername)
         local codeseq = fediauth.give_code(secret_b32)
 	fediauth.send_code(codeseq[1], fields.fediverse_account_url)
@@ -56,7 +66,7 @@ minetest.register_on_player_receive_fields(function(player, formname, fields)
 
         minetest.show_formspec(playername, FORMNAME, formspec)
 
-	end
+    end
 
     if fields.code then
         local playername = player:get_player_name()
diff --git a/settingtypes.txt b/settingtypes.txt
index a00cf94..15e8a2e 100644
--- a/settingtypes.txt
+++ b/settingtypes.txt
@@ -7,3 +7,7 @@ fediauth.api_token (Token for account) string
 
 # If no fediverse account - no access to server
 fediauth.fedi_required (Require Fediverse account for each user) bool false
+
+# Useful if remote instance blocked on service account server or any other reasons
+# Separated by comma
+fediauth.restricted_instances (Restrict instance domains) string example.com,another.example.com,