Here you can check if you have a guest account. When you click Check a new page will open looking like this
If your company is using Microsoft Office 365 you should be good to go. Otherwise you might need to create a Microsoft account using your company email. (See instructions on how to below.)
If you cannot log-on to the Nets Merchants Services IntraNets and get messages such as 'your account was not found', then you will have to create a Microsoft account using your company email address. That will have no impact on your current set-up, it is simply a technique used to ensure that we know that you have access to the mailbox.