Allow sender to immediately hangup after QUIT message

.github/workflows/docs.yml

@@ -17,7 +17,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        otp: ["24"] # https://www.erlang.org/downloads
+        otp: ["25"] # https://www.erlang.org/downloads
         rebar3: ["3.18.0"] # https://www.rebar3.org
 
     steps:

src/gen_smtp_client.erl

@@ -898,7 +898,10 @@ read_possible_multiline_reply(Socket) ->
                     Code = binstr:substr(Packet, 1, 3),
                     read_multiline_reply(Socket, Code, [Packet]);
                 <<" ">> ->
-                    {ok, Packet}
+                    {ok, Packet};
+                _ ->
+                    quit(Socket),
+                    throw({unexpected_response, Packet})
             end;
         Error ->
             throw({network_failure, Error})

src/gen_smtp_server_session.erl

@@ -829,7 +829,7 @@ handle_request({<<"NOOP">>, _Any}, State) ->
     send(State, "250 Ok\r\n"),
     {ok, State};
 handle_request({<<"QUIT">>, _Any}, State) ->
-    send(State, "221 Bye\r\n"),
+    try_send(State, "221 Bye\r\n"),
     {stop, normal, State};
 handle_request(
     {<<"VRFY">>, Address},
@@ -1358,6 +1358,14 @@ check_bare_crlf(Binary, _Prev, Op, Offset) ->
             end
     end.
 
+try_send(#state{transport = Transport, socket = Sock} = St, Data) ->
+    case Transport:send(Sock, Data) of
+        ok ->
+            ok;
+        {error, _Err} ->
+            ok
+    end.
+
 send(#state{transport = Transport, socket = Sock} = St, Data) ->
     case Transport:send(Sock, Data) of
         ok ->