fix: tell tls what the smtps server name is (#634)

courier/courier.go

@@ -49,7 +49,7 @@ func NewSMTP(d smtpDependencies, c configuration.Provider) *Courier {
 		ssl = true
 		sslSkipVerify, _ := strconv.ParseBool(uri.Query().Get("skip_ssl_verify"))
 		// #nosec G402 This is ok (and required!) because it is configurable and disabled by default.
-		tlsConfig = &tls.Config{InsecureSkipVerify: sslSkipVerify}
+		tlsConfig = &tls.Config{InsecureSkipVerify: sslSkipVerify, ServerName: uri.Hostname()}
 	}
 
 	return &Courier{