Occasionally, such pop-up blocking can affect legitimate websites and applications, including Outlook Web Access. OWA uses pop-up windows to remind you of calendar events.
Most web browsers will let you know when they have blocked a pop-up. Clicking the "This website attempted to open a pop-up window" type message will usually allow you to add your Outlook Web Access web address to the "pop-ups allowed" list.
Step 1: In the Tools menu, click Pop-up Blocker, then click Pop-up Blocker Settings.
Step 2: In the Address of Web site to allow box, type the URL of the Outlook Web Access site - e.g. exchange.livemail.co.uk.

Step 3: Click Add, then click Close.
Now, pop-ups from Outlook Web Access will be allowed but the pop-up blocker will continue to function as normal on other websites.