Sending email
Sending domains vs mailboxes
Two concepts that often get conflated — the difference and when each one matters.
Two objects come up constantly in the dashboard and the API: a sending domain and a mailbox. They look similar, they both involve DNS and addresses on your domain, and they are easy to mix up. Here is when each matters.
Sending domains#
A sending domain is a domain (or subdomain) that Bytloop is authorised
to sign outbound mail for. Verifying a sending domain means publishing
DKIM, SPF, and DMARC records so mailbox providers trust the mail we
sign on your behalf. Once verified, any address on that domain can
be used as the from on an API send.
You need a sending domain whenever you send email, transactional or otherwise. Set-up steps live in Verify a domain.
Mailboxes#
A mailbox is a specific address that receives mail and that a human
can open in the /mail inbox to read and reply. Mailboxes are
scoped to a workspace and each maps to exactly one address — for
example support@send.acme.com.
You need a mailbox whenever a person on your team should be able to read and answer replies. Set-up steps live in Receive email.
How they relate#
A mailbox sits on top of a verified sending domain. You cannot create
a mailbox on support@send.acme.com unless send.acme.com is already
verified for sending — the DNS proof is the same in both directions.
Conversely, plenty of sending domains have zero mailboxes. Backend
services that only send transactional email and never expect a reply
often have no mailboxes at all; replies to no-reply@send.acme.com
bounce (or vanish, depending on how the MX record is configured).
| Concept | Direction | You need one when… |
|---|---|---|
| Sending domain | Outbound | You send any email — API, broadcast, transactional. |
| Mailbox | Inbound + outbound-reply | A human should read and respond to messages at a specific address. |