I think I found out how to do it my self. The way I did it is to enable Pop3 access of exchange.

By default with exchange server (2003 I think) there is a pop3 service (under administrative tasks- services) which is off. I enabled this.

Then I made sure that the user I was login in have pop3 protocol enabled (on 2003 its under server management ->users->user name->properties->exchange features tab)

I also needed to make sure the basic authentication was working.

So under server management I go to Adv Mang.-> Exchange -> admin groups -> my admin group -> servers -> my servers -> protocols -> pop3 -> my virtual server -> right click -> properties -> authentication.

To make it work I need to choose basic authentication, with "requires ssl/tls" unticked. This last bit seems to make a security hole.

It would be good if OnTime would work with "Requires ssl/tls encryption" ticked, as this would be more secure.

If this is ticked then I get an error when testing with OnTime. 

I did find another site which suggested ways of setting this up to guaruntee a secure system - I haven't mentioned everything they do, so this might cause some security and/or other problems.