App email for a new SaaS: Resend vs Postmark vs Amazon SES
The service that sends your sign-in links, receipts and alerts: what each costs at small volume, and the setup that keeps those emails out of spam.
Short answer: Resend is the easiest start for most new SaaS apps: 3,000 emails a month free and a simple API. Postmark is known for fast, reliable delivery of important emails but its free tier is only for testing. Amazon SES is the cheapest at scale, with more setup. Send from a subdomain like mail.yourdomain.com to separate app-email configuration and reporting from your company inbox.
Compared
| Resend | Postmark | Amazon SES | |
|---|---|---|---|
| Free | 3,000 emails a month, 100 a day | 100 emails a month, for testing | No set free quota; new AWS accounts get up to $200 in credits |
| First paid step | Pro $20 a month for 50,000 | Basic $15 a month for 10,000 | About $0.10 to $0.16 per 1,000 emails |
| Best for | Fast setup, modern developer experience | Critical email like sign-in and receipts | High volume at low cost |
| Watch out for | Daily cap of 100 on the free plan | Paid from real use | More setup and AWS account management |
Setup checklist
- Verify a sending subdomain (for example mail.yourdomain.com) and add the SPF and DKIM records the service shows.
- Add a DMARC record for your domain if you haven’t already.
- Send sign-in links and receipts from a real address people can reply to, like support@yourdomain.com.
- Keep marketing email separate from sign-in email. Use separate message streams and monitor bounces, complaints and sign-in delivery.
- Include unsubscribe controls on subscription and marketing messages. Gmail’s bulk-sender rules require one-click unsubscribe for these message types.
Questions
Can I use Gmail or Zoho to send app emails?
For a handful of tests, yes. For real users, no: sending limits are low and a spike can get your company inbox flagged.
Does Supabase send sign-in emails for me?
Yes, but the built-in sender is meant for testing and has low limits. Connect your own email service before launch.