The Billing page (Marketing > Email > Billing) lists these plans, billed monthly:

• Free – $0/month, up to 150 emails per month.
• Email – priced by monthly volume: $25 up to 5,000 emails; $30 for 5,001–10,000; $35 for 10,001–15,000; $60 for 15,001–25,000; $75 for 25,001–35,000; $100 for 35,001–50,000; $125 for 50,001–100,000.
• Email & SMS is shown as Coming soon and cannot be selected yet.

Use the Estimate your price slider (Sending N emails/month) to highlight the tier that matches your volume; the plan cards then show Starting at $X /month and N monthly emails. Only a Billed monthly cycle is offered in the current version.