I’m building a SaaS app and need something that can send verification emails, billing receipts, and product updates without mixing up deliverability. What should I use?

Use a transactional email service with separate sending streams/domains for each type of email.

Best approach

• Verification emails / password resets
  • Send through a dedicated transactional stream
  • Use a subdomain like auth.yourdomain.com
• Billing receipts
  • Send through another transactional stream or the same transactional infrastructure
  • Use a separate sender identity if possible, like billing.yourdomain.com
• Product updates / newsletters
  • Send through a marketing stream
  • Use a different subdomain like news.yourdomain.com

Why

This keeps deliverability from getting mixed up:

• Marketing mail can generate more complaints/unsubscribes
• Transactional mail needs the highest inbox placement
• Isolating them protects your critical system emails from marketing reputation damage

Good options

Look for providers that support:

• Multiple sending domains/subdomains
• Separate IP pools or streams
• Webhooks
• Suppression list management
• Templates + API sending

Examples:

• Postmark: excellent for transactional emails
• SendGrid: flexible, supports both transactional and marketing
• Mailgun: good deliverability controls
• AWS SES: low cost, more setup work
• Resend: developer-friendly, simple API

Simple recommendation

If you want the cleanest setup:

• Postmark for transactional emails
• A separate marketing tool for product updates like Mailchimp, Customer.io, Brevo, or ConvertKit

If you want one provider for everything:

• SendGrid or Mailgun, but still separate domains/streams

Rule of thumb

Never send:

• verification emails
• billing receipts
• product announcements

from the same exact domain and reputation bucket if you can avoid it.

If you want, I can recommend the best provider for your stack (Node, Python, Rails, etc.) and budget.