Using classic Outlook for Windows in business environments
Based on your description and the additional information you've provided, the key point is that Outlook for Windows does not have a built-in mechanism to automatically shrink or reflow an oversized HTML table to fit an A4 page during printing. If the table is already cut off in Print Preview, Outlook has typically rendered the content that way before it is passed to the printer.
One thing still worth testing is changing the page size in Print Options > Page Setup to A3 (if available) and then checking whether the table appears fully in Outlook's preview. If it does, the next step would be to look in the printer driver's Properties/Preferences for a scaling feature such as Fit to Page, Scale to Fit, Reduce/Enlarge, or an A3 > A4 reduction setting. Those options are provided by the printer driver rather than Outlook itself and vary by manufacturer.
If the content remains clipped in Outlook's preview even when A3 is selected, the behavior is occurring within Outlook before the content is sent to the printer. In that case, Outlook does not provide a supported setting to automatically scale the table to fit an A4 page.
As an additional test, does the same behavior occur when printing to Microsoft Print to PDF? If the table is also clipped there, that would further indicate that Outlook is rendering the content this way rather than the printer driver causing it
I hope this information helps.