It depends on the type of settings you currently have loaded.
What you would have to do is open up your connection settings in Lotus Notes (there should be a pop up window for this in the lower right hand corner of Lotus Notes). If you click on it you will be able to select different profiles, or pick Edit Current. If you have a 'local' one listed there just select that.
Otherwise you would have to select Edit Current, navigate to the mail tab, and change your mail file location to Local instead of server.
Also, you would have to send mail from the Local copy of your mail database and not the server copy (if they offer one)
I don't have Lotus in front of me right now so I can't provide any screenshots. It may vary from company to company and how they set up their Mail.
A bit off topic, but I also had the (crappy) Notes R5 in my work, and managed to find a connector that allows you to connect with Outlook 2003 to the Domino (Notes) servers. If you need guidance with this, give me a beep here.
Ep, glad to see you come back and tidy up...did want to ask a one day favor, I want to enhance my resume , was hoping you could make me administrator for a day, if so, take me right off since I won't be here to do anything, and don't know the slightest about the board, but it would be nice putting "served administrator osnn", if can do, THANKS