The sandbox sender
You can send your first email before you own a domain, before any DNS change, and before anybody in another department answers a ticket.
Every new account may send from an address we own and have already verified:
onboarding@<our sandbox domain>
The dashboard’s checklist shows the exact address for this deployment — do not compose it yourself, because it is configuration and it differs between deployments. An account with no sandbox configured sees the field empty, which is the signal that this feature is off here.
Two rules, and they are the whole thing
The From is ours. You are not claiming an identity, you are borrowing
ours — which is exactly why no verification step is needed.
The To can only be one of four test addresses, listed below. They reach
Amazon’s mailbox simulator, so a sandbox message is never delivered to anybody —
not to a stranger, and not to you either.
That sounds like a limitation and is mostly a favour. A shared sender has no sending reputation of its own, so mail from it is the mail most likely to be filtered — and a message you had to dig out of a spam folder teaches you nothing about what your own domain will do. Sending to the simulator gives you the part that is actually informative, immediately and identically for everybody: a real message, through the real provider, with real events coming back.
The four addresses
| Address | What happens |
|---|---|
delivered@ | Delivers. The default the dashboard’s snippet uses. |
bounced@ | Comes back as a hard bounce, with a real bounce event, Amazon’s own classification and its diagnostic text. |
complained@ | Comes back as a spam complaint. |
suppressed@ | Lands on your suppression list, so you can watch the next send to it be refused before it costs anything. |
All four are on the sandbox domain — bounced@<our sandbox domain>, not
bounced@ anywhere else.
This is how you build and test bounce handling without needing an address that really bounces. Nothing here reaches an inbox, so none of it touches your sending reputation.
There are ten sandbox sends per account, for its lifetime. It is not a reputation guard — nothing can be complained about — it bounds a shared sender being used as a permanent free one, and a script left running against it. The dashboard shows what is left; past that, the answer is to connect a domain.
Watch the timeline, not your inbox
Open the message in the log. sent appears when the provider accepts it,
delivered when the notification comes back, and a bounce or complaint arrives
the same way a real one would — through the same webhook and the same timeline
your production traffic will use. That is the thing worth seeing, and it is the
thing a happy-path email in your inbox does not show you.
It is a restriction, not a convenience
Until you have a verified domain this is the only From available, and those
four are the only To — the sandbox replaces “you cannot send yet” with “here is
what you can send”, at the same enforcement point.
Once a domain of yours verifies, send from it and reach anybody: the restriction is gone, along with the reputation problem, because the reputation is then yours.