Better guide the SMTP only by a remark in the SMTP only block. "Use API keys for SMTP User / SMTP Password"
My misunderstanding was due to the lack of SMTP User / SMTP Password mentions
until I guessed to take the APY keys for that
A suggestion : put a remark in the SMTP only block. "Use APY keys for SMTP User / SMTP Password"
Also, I was confused because the read-only fields of the SMTP only block appeared so grayed that I took them as placeholders (I use the dark mode)