An exchange server is so that you can host your own email. With only 5 computers/users its probably not worth the cost and hassle of setting one up if you have no experience with it.
If, in Outlook, you go Help ->About it probably shows that you have the Corporate or Workgroup edition installed.
The following applies to Outlook 2000 but would be similar for later versions.
If you go Tools ->Options and click on the Mail Services tab it probably indicates to check for new mail on M$ Exchange Server. To change it now to "Internet Only" which is what you need do the following:
1. Go to the Mail Services tab as above and click "Reconfigure Mail Support"
2. Select "Internet Only" and follow the Wizard
There are some gotchas if you have already used Outlook in the Corporate or Workgroup Edition mode. The following is from Outlook's help using "Workgroup" as the keyword:
About changing e-mail configurations
Microsoft Outlook can use either dial-up Internet service, corporate e-mail servers, or both.
When to use the Internet Only option
If you use a modem to make a dial-up connection to an Internet service provider, and you're not connected by means of a LAN to a server, select the Internet Only option. This configuration optimizes your e-mail for POP3/SMTP or IMAP4. The Internet Only option offers significant performance benefits for dial-up users. If you select this option, you'll need to use the Symantec Fax Starter Edition fax program.
When to use the Corporate or Workgroup option
If you work on a LAN running Microsoft Exchange Server, Microsoft Mail 3.x, Lotus cc:Mail server, or you use Classic MSN (version 1.x, which came with Microsoft Windows 95), select the Corporate or Workgroup option. By using the Internet E-mail service provider, you can also use Internet service providers that offer the POP3/SMTP protocol. You can also use LDAP Internet directories. If you select this option, you will need to use the Microsoft At Work fax program.
What happens when you change your e-mail configuration
When you change your e-mail configuration, the files that support specific e-mail functions are replaced. Some Outlook features will be affected when these files are changed. The list below shows which features are affected by changing your e-mail configuration.
What you need to do:
Fax: Reinstall the fax program for the configuration you use. Microsoft At Work fax is available only for Corporate or Workgroup configuration. The Symantec Fax Starter Edition fax program must be used for the Internet Only configuration.
Contact links: Re-create any links to contacts that come from address books other than your Contacts folder.
Distribution lists: Re-create any addresses in distribution lists that come from address books other than your Contacts folder.
Notes:
If you are not sure which configuration you have, on the Help menu, click About Microsoft Outlook.
If you change from the Internet Only option to the Corporate or Workgroup option, you will need to add Microsoft Exchange or another mail service to your profile. On the Tools menu, click Services, and then click Add.
By default, your mail will be delivered to a .pst file on your computer. To change the location of where your mail is delivered do the following: After you add the mail service to your profile, in the Services dialog box, click the Delivery tab, and then select the location where you want new mail to be delivered.
Hope this helps.
