If the email addresses are visible in Excel but disappear only when you print or use Print Preview, this is usually caused by the print area, scaling, or page setup, rather than the email addresses themselves.
Go to File > Print and look at the preview. Check whether the email column is missing entirely or being pushed onto another page.
Go to File > Print > Settings and choose Fit All Columns on One Page. This is often the quickest fix when the email address column is simply falling outside the printable width.