I can receive but not send emails using Outlook 2010 under Windows 7. Works fine in webmail. I've used Outlook with Norton 360 for many years with no problem. This problem just started this week out of the blue. I tried temporarily disabling the Norton firewall and outgoing mail virus scan, but still had the problem. I don't think there's a virus or software corruption or problem with the settings because the same problem also just began occurring on my old computer which uses Outlook 2003 under Windows XP. The odd thing is if I don't use my email for several hours, it seems to 'self correct'. I can then send a few emails, then the problem returns. I get the message: "server error: '451 Outbound mail refused".
Could there be some other feature of Norton 360 that is preventing the emails from getting out?
If no, any other ideas?