[PATCH 2/2] pop3: implement IN-USE from RESP-CODES (RFC 2449)

[Eric Wong]

This may help clients communicate to users if they're
making parallel connections or if we have server bugs.
---
 lib/PublicInbox/POP3.pm | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/PublicInbox/POP3.pm b/lib/PublicInbox/POP3.pm
index f920571d..5cffc556 100644
--- a/lib/PublicInbox/POP3.pm
+++ b/lib/PublicInbox/POP3.pm
@@ -176,7 +176,7 @@ sub _login_ok ($) {
                $self->{uid_max} = $self->{ibx}->over(1)->max;
                \"+OK logged in\r\n";
        } else {
-               \"-ERR unable to lock maildrop\r\n";
+               \"-ERR [IN-USE] unable to lock maildrop\r\n";
        }
 }
 
@@ -350,6 +350,7 @@ USER\r
 PIPELINING\r
 UIDL\r
 EXPIRE 0\r
+RESP-CODES\r
 .\r
 EOM
 }