smtp-check: Add a -skip_tls_check flag

This patch adds a -skip_tls_check flag, so smtp-check can still be used
from places where outgoing SMTP connections are blocked.

cmd/smtp-check/smtp-check.go

@@ -17,6 +17,8 @@ import (
 var (
 	port = flag.String("port", "smtp",
 		"port to use for connecting to the MX servers")
+	skipTLSCheck = flag.Bool("skip_tls_check", false,
+		"skip TLS check (useful if connections are blocked)")
 )
 
 func main() {
@@ -56,6 +58,9 @@ func main() {
 			}
 		}
 
+		if *skipTLSCheck {
+			log.Printf("TLS check skipped")
+		} else {
 			c, err := smtp.Dial(mx.Host + ":" + *port)
 			if err != nil {
 				log.Fatal(err)
@@ -75,9 +80,11 @@ func main() {
 			log.Printf("TLS OK: %s - %s", tlsconst.VersionName(cstate.Version),
 				tlsconst.CipherSuiteName(cstate.CipherSuite))
 
-		log.Printf("")
 			c.Close()
 		}
 
+		log.Printf("")
+	}
+
 	log.Printf("=== Success")
 }