One of my users bought an ibook for home use, running OS X. She's unable to open her webmail when logging in to our Exchange server. She supplies the url, is prompted for her username,password,domain, but once entered correctly she receives a page that tells her she is not authorized. When doing this exact process through her PC she doesn't have a problem. Any thoughts I may be able to help her with? Thanks in advance.

Maybe the site uses Windows-specific code in its log-on/validation page? (Wild guess...) If she is (wisely) using a browser other than IE, she could try the site using IE to see if it gives any different results. She could also try checking the browser settings to make sure everything's enabled (JavaScript, pop-ups maybe?) and get it to show JavaScript errors in case there are more clues there. Might also be worth checking with the site administrators in case they are aware of a limitation.

problem solved. Microsofts newest version of Internet explorer (6.0) on macs have a problem with Microsofts Exchange 5.5 server. We downgraded to 5.5 and no problem. Thanks for your help. Hope this post addes some insight to others have this problem.