Ok, bad news. After waiting for the cron execution day (yesterday) I can confirm that adding this code didn't solve the issue. And even worst news, it seems is not only a email issue, but a general failure. I track the incoming traffic to my sites and normally when Sitemaps is executed I see the hits generated by the software crawling the site. In this case there are no hits from it. Please is there a way to get an older version of the script? I don't have these problem with the previous versions.