Best Practices What to Do When Users Don’t Receive Their Transactional Emails By MailChannels | 4 minute read You’ve built the flow. The form was submitted. The API sent the message. But the user says they didn’t get the email. If you’re responsible for transactional email, password resets, signup confirmations, security alerts, this scenario is all too familiar. When users don’t receive their transactional emails, it creates friction fast. Whether it’s frustration from being locked out of an account or anxiety about a missing purchase receipt, the pressure is on to fix it, quickly and reliably. This blog walks you through a step-by-step approach to diagnosing the issue and ensuring future messages land as expected. Step 1: Confirm the Message Was Sent Before diving into logs or filters, verify that the email event was triggered. Was the email triggered by the application logic (e.g., after form submission)? Did your system enqueue and send the message through your email provider or SMTP relay? Can you find the message ID, timestamp, or recipient address in your delivery logs? If the email was never sent, you’re looking at an application or integration bug, not a deliverability issue. Step 2: Check the SMTP Response or API Result If the message was handed off to your email service provider, inspect the SMTP response or API status. A 202 Accepted or 250 OK typically means the message was accepted for delivery. A 4xx error indicates a temporary issue (e.g., greylisting or throttling). A 5xx error means the recipient server rejected the message outright. → See: Diagnosing SMTP 5xx and 4xx Error Codes Log entries and API responses should include a delivery status, message ID, and sometimes even bounce details. Step 3: Analyze the Email Header (If Available) If the user eventually received the email or if you can send a test to your own inbox, review the email’s header. Look for: Delivery path (Received lines) Authentication results (SPF, DKIM, DMARC) Spam scores or filtering metadata Message ID for correlating with logs → Read: How to Read an Email Header (with Real Examples) Headers often reveal delays, authentication failures, or signs of spam filtering that aren’t visible to end users. Step 4: Ask the User to Check Their Spam Folder It seems obvious, but users often skip this. Encourage them to: Check spam or junk folders Search for your sender name or domain Look in “Promotions” or “Updates” tabs (especially in Gmail) Whitelist your sending address if it was misclassified If the message landed in spam, you likely need to review your sender reputation or authentication setup. → Try: Tools to Test Transactional Email Deliverability Step 5: Validate Authentication and DNS Records Mail providers use SPF, DKIM, and DMARC to verify that your email is authorized and trustworthy. If these are misconfigured, your messages may be blocked or downgraded. Use a domain authentication tool to check: Is SPF passing and aligned? Is the DKIM signature valid? Does your domain have a DMARC policy? → Check out: SPF, DKIM, and DMARC for Transactional Email Step 6: Monitor Delivery and Bounce Events If you have access to bounce or delivery webhooks, use them. They’ll tell you in real time whether messages were accepted, bounced, or deferred, and why. Set up monitoring to track: Bounce rates over time Authentication failures Latency or delay spikes Patterns by recipient domain (e.g., Gmail vs Outlook) → Learn more: How to Monitor Email Performance (Delivery, Opens, Errors) Step 7: Retry or Resend the Message (if Safe) If the message was never delivered, consider re-sending it, but only once. Avoid retry storms that look spammy to mail providers. For messages like account verification or password resets, give users the ability to request a resend on demand. Step 8: Escalate to Your Email Provider (if needed) If you’ve ruled out your app logic, validated delivery, checked authentication, and still can’t resolve the issue, it may be time to escalate. Your email service provider (like MailChannels) can help investigate: IP reputation issues Domain blocks at specific ISPs Spam filter triggers or authentication anomalies Be ready to share: Message headers (if available) Message ID or timestamp SMTP response or API status Recipient domain and address Related Resources How to Use Postman with the MailChannels API How to Monitor Email Performance (Delivery, Opens, Errors) Tools to Test Transactional Email Deliverability Diagnosing SMTP 5xx and 4xx Error Codes Turn User Complaints Into a Deliverability Workflow When a user says they didn’t get your email, it’s not just a support ticket, it’s a signal to improve visibility into your delivery pipeline. The best teams turn these moments into repeatable workflows with clear monitoring, authentication, and fallback strategies. Want to simplify this process with built-in diagnostics and delivery intelligence? Get started with MailChannels Transactional Email and deliver with confidence, every time.