The notification did not arrive, and the spam filter was not the first suspect.

Start with the record, not the inbox

An inbox is a lossy view of reality. It merges everything that reached that address, hides what was filtered, and gives no indication of what never left. The dashboard does the opposite: one row per submission, with its delivery attempts attached. Open the row before opening the mailbox.

Cause one: the recipient was never verified

A verification email is sent when a recipient is added. Until that link is clicked, notifications for that form are queued as pending. This is deliberate: it prevents someone pointing a form at an address they do not own and using the form as a mail relay. The consequence is that a freshly configured form can accept a real submission and send no mail, which looks like a bug and is actually the safety interlock.

Cause two: the sender domain is missing its records

Receiving providers judge the domain in the envelope, not the form. Three records matter: SPF, which says which hosts may send for the domain; DKIM, which signs the message so it can be verified as unmodified; DMARC, which tells the receiver what to do when the first two disagree. A bring-your-own SMTP domain without these sends worse than the shared default, because it is a new domain with no history and no authentication.

Cause three: the address is suppressed

A hard bounce means the mailbox does not exist. A complaint means the recipient pressed "report spam". Either one adds the address to the suppression list, and further sends to it are skipped. That is correct behaviour — continuing to mail a complaining address is how a sending domain loses its reputation — but it means a colleague who once bounced will silently stop receiving notifications until the suppression is removed.

Cause four: it arrived and was filed

Notifications are transactional mail with a plain subject and a body assembled from the submitted fields. A filter that looks for marketing language will not catch them, but a filter keyed on the sender address will, and a mailbox rule that moves anything from a no-reply address to a folder will too. Before assuming anything exotic, search the mailbox for the submission id from the delivery log.

What makes delivery debuggable

Every attempt is recorded with a timestamp and the provider's response, and the retry button re-queues a failed channel rather than making you re-submit the form. That is the difference between a claim and an instrument: you can see the refusal, quote it, and fix the cause.