Provider guide · Brevo
Brevo, the former Sendinblue, keeps a real free allowance, which makes it the default answer for small WordPress sites. Its two surprises: the SMTP login is a generated address that is not your account email, and brand-new accounts need transactional sending switched on once.
1 · Credentials
Everything WordPress needs sits on a single page of the Brevo dashboard, under the SMTP tab. The only trap is grabbing the right kind of key.
One prerequisite for fresh accounts: Brevo activates transactional sending on request, so an account that has never sent transactional email may need to ask support to switch SMTP on. It is a one-time formality, but a blocking one, and better discovered today than at your first failed contact form.
In Brevo, open the account menu at the top right, then SMTP & API, then the SMTP tab.
It looks like 7ab…@smtp-brevo.com: a technical identifier Brevo generates for you, deliberately not your account email.
From the same SMTP tab, generate the key and copy it immediately; the full key is displayed once. An SMTP key is not the same thing as an API key, and the API key will not authenticate SMTP.
Under Senders, domains & dedicated IPs, validate the address WordPress will send from, or authenticate the whole domain with the DNS records Brevo provides. The From you configure later has to be covered by one of the two.
2 · In the plugin
Selecting the Brevo preset fills the server (smtp-relay.brevo.com), the port (587) and the encryption (TLS). What remains is yours.
The generated @smtp-brevo.com login from the SMTP tab.
Your SMTP key.
A sender you have validated in Brevo, on your own domain. Never the @smtp-brevo.com login; it is an identifier, not a mailbox.
Save, then use Send Test Email. If it authenticates but the message is refused, the sender address is the suspect: it has to exist in Brevo’s validated senders, or be covered by your authenticated domain.
3 · Pitfalls
Brevo’s hurdles are all about sender identity, and they got stricter when the big mailbox providers changed the rules for everyone in 2024.
Older tutorials say to sign in with the address you use for the Brevo dashboard. Current accounts get a generated login ending in @smtp-brevo.com, shown on the SMTP & API page, and that is the value the username field wants. Wrong login, and the error is the same “could not authenticate” a wrong key produces.
Since the Gmail and Yahoo sender rules of 2024, Brevo pushes hard on domain authentication: the Brevo DNS code, DKIM and DMARC records added at your registrar. Send from a free webmail address, or from a domain you never authenticated, and Brevo may rewrite your sender into something like you@…brevosend.com, which your recipients will read as suspicious. Authenticate the domain once, under Senders, domains & dedicated IPs, and the problem never comes back.
The free allowance is around 300 emails a day, resetting daily, with Brevo queueing a bounded overflow and dropping the rest. Comfortable for forms and order confirmations on a small site; a store having a big day can hit it. The plugin’s own volume alerts make a decent early warning that you are approaching the ceiling.
The email log keeps the exact error message the server returned, which is the fastest route to the cause. The documentation walks through the common ones.
There is a guide like this one for each of the twelve presets, from Gmail to Amazon SES, and the plugin takes any other SMTP server too.