Hello,
Why was this marked as “Resolved”?
This does not seem to be an issue with Brevo, but with the latest version of WP Mail SMTP (4.0.1).
I updated today and it no longer worked, with everything else checked and being correctly configured.
The issues just solved by reverting back to Version 3.2.1, which I currently had in place for the particular site where I made the update.
Testing with a clean, up-to-date environment, on the same host and with the same Brevo account, the same behavior can be observed. Version 3.2.1 works just find, while Version 4.0.1 results in the error mentioned in this thread.
I did not yet test other versions in-between 3.2.1. and 4.0.1, but I will proceed to do so and see which one is the latest that works.