This problem is apparently causing emails sent via Spark / Xtra /Yahoos SMTP server, to bounce back with the following error 550 5.7.1 You are not authorized to send as  name@yourdomain.co.nz Apparently this is due to Spark currently being in the process of moving to a new email provider. A temporary fix for this is to send out your email directly via Yahoos SMTP server setting. So this means changing your outgoing SMTP server setting from send.xtra.co.nz , to smtp.mail.yahoo.com . In most cases this should work, at least temporarily, until Yahoo deactivate this, and until Spark come up with a local solution. We do also suggest contacting Spark and raising a ticket with them, as the more people that report this problem to them, the more likely they will fix it properly. Apparently people are having other problems to with the Spark email service during the migration, so this fix above may not help with those problems. If you use the Lounge Network for your email, you don’t