While the above is certainly correct there is a workaround but it is messy and you need to be careful.
You'll need to follow the same procedure constantly and never deviate from it if you do this or you will miss some of the E-Mails on the NB. Setup Outlook Express to collect the incoming E-Mails and then open Tools, Accounts highlight your Mail account and click on Proprieties and then go to Advanced and tick Leave copy of messages on Server. That way you can download your E-Mail on the NB and leave it on the mail server until you log on with the Desktop machine which will then empty your mail box. But if you use the Desktop unit first there will be nothing for the NB to pick up.
There is one other Option and that is to share the E-Mail Folder on the Desktop and then Import across the network into Outlook Express using the Import tool.
If you use the former you'll be able to pickup E-Mail while away from home on the NB and not run the risk of loosing any e-mail if the NB gets damaged/stolen which happens quite a lot as it will still be there waiting for you when you get home.
The down side to this is that you have limited space in your Mail Box and if you do not use the Desktop for several days you'll be constantly downloading the same e-mail until you use the Desktop to empty your mail box. If you get a lot of incoming e-mail as well you run the risk of allowing your Mail Box to fill up and then you'll stop getting new messages as they are sent and those who send you messages will get a underivable message sent to them with Mail Box Full on it.
Col