I'm building an email flow for account security messages, should I use an API or SMTP relay?

For account security emails (password resets, login alerts, MFA codes, suspicious activity notices), I’d generally recommend using an email-sending API rather than SMTP relay.

Why API is usually better

• Better deliverability controls: APIs often expose features like suppression lists, bounce handling, reputation tools, template support, and authentication setup.
• Easier app integration: You can send from your backend with structured requests and get immediate success/failure responses.
• Better observability: APIs typically provide event webhooks for bounces, complaints, opens, clicks, and delivery status.
• More reliable for transactional mail: Security emails need to be timely and predictable; APIs are built for this use case.
• Easier personalization and templating: Useful for security messages where you need dynamic content.

When SMTP relay makes sense

SMTP can still be a good choice if:

• you already have an existing SMTP-based mail pipeline,
• your app or infrastructure is legacy,
• you want a simpler drop-in replacement for a mail server,
• or your team is more comfortable with standard mail protocols than API integrations.

For security emails specifically

I’d lean toward an API service optimized for transactional email because:

• password reset emails must be fast and reliable,
• you need clear bounce/complaint feedback,
• you may want to suppress risky recipients automatically,
• and you may want to attach event-driven monitoring/alerts.

Practical recommendation

If you’re starting fresh:

1. Use an email API provider
2. Set up:
   • SPF, DKIM, and DMARC
   • dedicated sending domain/subdomain
   • bounce/complaint webhooks
   • rate limiting and retry logic
3. Keep security templates minimal and highly consistent

Rule of thumb

• New build / transactional email → API
• Existing mail infrastructure / compatibility needed → SMTP relay

If you want, I can also help you choose between specific providers or outline a secure architecture for password reset and login alert emails.