Email marketing uses email to stay in touch with an audience. Common formats include newsletters, product announcements, and invitations. The content, audience, and sending frequency depend on the campaign’s purpose.

How do email formats differ?
A newsletter is a recurring format. An invitation can be a one-time campaign. A welcome email can follow a signup automatically. An order confirmation relates to a specific transaction and serves a different purpose from a marketing campaign.
Example from signup to reporting
A company offers a monthly industry newsletter. Interested readers sign up through a form and confirm their address. The team sends the issue to the intended list and then checks clicks, unsubscribes, and delivery errors. The useful metric depends on the goal. For an invitation, registrations can tell you more than recorded opens.