When a WHMCS email is missing, trace it from the application to the sending provider and then the destination. This establishes whether the message was never generated, failed submission or was accepted and later filtered.
01 Trace one specific message
- Identify the intended recipient, message type, related invoice or ticket and approximate send time.
- Check the client's email history or System Logs for the relevant message. Some sensitive authentication templates are intentionally absent from the ordinary email message log.
- Confirm that the triggering event occurred and that outgoing mail or the relevant template is not disabled.
- If submission failed, test the configured mail provider and inspect its short diagnostic output.
- If submission succeeded, search the provider's delivery events using the recipient and message identifier.
- Check the destination's spam, quarantine and rejection information. Correct the identified sender, authentication or address problem before resending.
02 Check sender differences
A billing email and a support reply may use different From addresses. Verify that the provider permits each sender and that the domain's mail authentication follows the provider's current instructions. Changing unrelated DNS records without checking the actual sending route can make delivery worse.
For scheduled messages, confirm that cron uses a compatible PHP environment and has the same required network access. A manual message sent from the browser may succeed while a scheduled task fails.
Common questions
Can a Sent entry prove the customer read the email?
No. It is evidence of the application's sending activity, not proof of inbox placement or reading.
Should staff repeatedly resend an invoice?
First confirm its current balance and fix the delivery issue. Repeated copies can confuse customers, especially if payment was already received.
What evidence should go to mail support?
Provide the timestamp, sender, recipient, message identifier and redacted error or delivery status. Keep credentials and unrelated customer messages out of the report.