When setting up Microsoft Outlook to access your mailbox on our email servers we recommend you use secure settings. You can find your email server settings in your space summary in the hosting control panel. They will be similar the following host names, which are used for both incoming and outgoing (SMTP) servers.
m.nahosting.uk - easier to type in on mobile devices
It is possible to use mail.yourowndomain.com if you really want to, but if you want to use a secure connection and receive no warnings about the security (SSL) certificate then you must use the hostnames ending with .nuttyabouthosting.co.uk or .nahosting.uk.
Under "More Settings ..." on the "Outgoing Server" tab.
On the "Advanced" tab.