Your application receives a successful response from the email API, but the customer says the receipt never arrived. These observations can both be true. A request passes through several systems, and a success at one stage does not establish success at every later stage.
Start with the application request
A validation error means the request needs attention before normal processing can continue. Authentication errors point to credentials or account access. These are different from a valid request that has been accepted for sending or scheduled for later.
In Sendar, inspect the response body and returned status as well as the HTTP code. Store the message ID with your application event. Without that link, support teams may have to search by recipient and time, which becomes ambiguous when several messages were submitted.
Understand provider acceptance
A sent state indicates provider acceptance in Sendar's documented flow. It is not a statement that the email appeared in the primary inbox or that the reader opened it. The recipient system may apply additional filtering, or a later event may report a bounce.
Scheduled messages are another useful distinction. A record created for a future time is pending work, not evidence that transmission has already happened. Your application's wording should reflect that difference.
Investigate with a timeline
When a customer reports a missing message, start with the business event, then locate its Sendar record. Inspect available events and error details. Check the recipient address and the sender domain. Ask the recipient to check filtering only after you have established what your own system did.
Do not automatically resend merely because a user did not see the first message. A duplicate password reset or receipt can create more confusion. If a deliberate resend is appropriate, record that it is a separate action and use the corresponding application policy.
Make monitoring match the promise
Track request failures, accepted messages, available delivery events and complaints as distinct signals. An acceptance-rate chart is useful, but label it accurately. Keep customer-facing copy equally precise: “We have requested your receipt email” describes less than “Delivered to your inbox,” and the stronger statement requires stronger evidence.