To build a SaaS that sends emails for clients using your services (SMTPwire, WarmupSMTP, DedicatedSMTPserver):

1. Set up SMTP backend (yours or allow client’s)

2. Create web dashboard (login, campaigns, stats)

3. Add domain auth (SPF, DKIM, DMARC setup)

4. Build email editor + scheduler

5. Use job queues for sending control

6. Show analytics (opens, clicks, bounces)

7. Add billing system for plans

8. White-label for resellers

Done right, it runs fully on your own infra — high control, high margins.