No. An email address is not required. For a Vendor, business, or company for which you do not know an email address:

• Go to People.
• Search by the Vendor Tag and select the entity/person's profile.
• Click Edit this Contact button in the upper right.
• A toggle switch Contact is a company appears. Turn that ON and a check box will appear under the email address of the contact that says Email not known. Check that box if you don't have an email address.
• Save.