# Transactional Email — Troubleshooting Guide

**Document Version:** 1.0.0 (Phase 15)

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## Common Issues & Resolutions

### 1. Connection Error / Authentication Failed
- **Symptoms:** Test email displays *"Could not connect to SMTP server"*.
- **Checks:**
  - Verify SMTP hostname (e.g. `smtp.mailgun.org`, `smtp.sendgrid.net`).
  - Check port & encryption match (`587` for `TLS`, `465` for `SSL`).
  - Verify API key or username/password is active with your mail provider.

### 2. From Address Disallowed
- **Symptoms:** Provider rejects message with sender domain validation error.
- **Checks:**
  - Ensure `From Email` domain is verified and authorized in your SMTP provider account (e.g. SPF/DKIM configured).

### 3. Rate Limit / Quota Exceeded
- **Symptoms:** Follow-up status becomes `failed` after high volume.
- **Checks:**
  - Review your provider's hourly/daily sending quota.
  - Follow-up jobs automatically retry with exponential backoff up to 3 attempts.