we need to move off SMTP because it keeps failing

If SMTP is repeatedly failing, the safest move is usually to stop depending on direct mail delivery from your app and switch to a dedicated email delivery service or an indirect workflow.

Here are the best options, depending on what you’re sending:

1. Use an email API provider instead of SMTP

These are usually more reliable than raw SMTP and give better logs, retries, and deliverability.

Common choices:

• SendGrid
• Mailgun
• Amazon SES
• Postmark
• Brevo

Typical benefits:

• Better deliverability
• Fewer auth/TLS issues
• Retry handling
• Bounce/complaint tracking
• Easy API integration

2. Use a queue + worker for email sending

If the problem is intermittent failures, don’t send mail inline from your app.

Pattern:

• App creates an email job
• Job goes to a queue
• Worker sends it asynchronously
• Retry on transient failure

This avoids user-facing failures and lets you control backoff, dead-lettering, and observability.

3. If you must keep SMTP temporarily

Hardening SMTP can reduce failures:

• Ensure STARTTLS/SSL config is correct
• Verify port 587 vs 465 vs 25
• Check provider auth requirements
• Add retries with exponential backoff
• Log full SMTP response codes
• Validate DNS, SPF, DKIM, DMARC
• Monitor IP reputation

4. Decouple email entirely

If the emails are critical notifications:

• Write events to a durable store
• Have a separate notification service send them
• Allow fallback providers
• Track delivery status independently

Recommended migration path

1. Pick an email API provider
2. Move one email type first
3. Add queue/retry logic
4. Monitor bounce/failure rates
5. Turn off direct SMTP once stable

If you want, I can help you choose the best replacement based on your stack, volume, and whether these are transactional emails, marketing emails, or alerts.