Sounds like a name resolution (DNS) problem
in the outlook account box you will have an entry for your mail. This maybe an IP address or as is usual a DNS name eg
mail.freeserve.co.uk.(made up name)
The first thing to do is confim it is a resolution issue by pinging the account server from DOS. (MSDOS PROMPT)
eg ping mail.freeserve.co.uk
This will tell you if it is a network problem or a mail problem.
The next step depends on the result of this ping test and can get complicated, but at least you will know where the problem is and you can e-mail me for more help.
In the meantime you should have a facility with your provider to get your e-mail using a web browser.
BTW e-mail is a very weak link in security.