Mail: connections with wrong ALPN protocols are now rejected. This is a recommended behavior by RFC 7301 and is useful for mitigation of protocol confusion attacks [1]. For POP3 and IMAP protocols IANA-assigned ALPN IDs are used [2]. For the SMTP protocol "smtp" is used. [1] https://alpaca-attack.com/ [2] https://www.iana.org/assignments/tls-extensiontype-values/

--- a/src/mail/ngx_mail.h
+++ b/src/mail/ngx_mail.h
@@ -324,6 +324,7 @@ typedef ngx_int_t (*ngx_mail_parse_comma
 
 struct ngx_mail_protocol_s {
     ngx_str_t                   name;
+    ngx_str_t                   alpn;
     in_port_t                   port[4];
     ngx_uint_t                  type;