There are several ways to communicate between PCs on the same network:
Network 'pings'
Windows Messaging
Win Pop-up
Email via a Network 'PostOffice'
None of the above require external services and can be implemented relatively easily, depending upon the Operating Systems available.
For Windows 98 systems and above, running Winpopup.exe from the command line (or having it in your Start Menu) allows you to instantly 'message' any recognised 'Logee' on the network. Useful if you don't want the fuss and epense of eMail but just want a quick internal system.
It pays to think about how communications can be managed, monitored and facilitated before just diving head-first without considering future needs and possible abuses of the system.
Many 'Office' applications include the useful File-Send To command. These are specific to MS Office and depend upon how each system is set up: You may be able to send an active document to:
Mail Recipient: Opens a routing window on your screen and lets you select a name or names from your Outlook address book, type a subject line, and then e-mail the document.
Mail Recipient (as Attachment): Similar to Mail Recipient, but sends the document as an attachment, rather than as the body of the message.
Routing Recipient: Opens a dialog box that lets you select a list of people from your Outlook address book to whom the document will be sent. You can choose to send it to all recipients simultaneously or individually, and you can configure the document to automatically return to you when each recipient completes their work. You can also track the status of its routing and add a separate message for comments or instructions.
Exchange Folder: If you use Microsoft Exchange on your network, this command lets you choose a folder in which to publish the document.
Fax Recipient: If your system includes fax services, this command runs the Fax Wizard, which walks you through the process of sending your document as a fax, with or without a cover sheet.
Microsoft PowerPoint: This Word command sends the document to PowerPoint, where it becomes the outline for a presentation.