CC and BCC not working

I take it that the purpose of inserting CC and BCC message header fields in the “Additional headers” setup field is to send submitted forms to further recipients as specified in the CC or BCC fields, and not just to the recipient specified in the “To” field?

That seems correct, according to this support page and this other support post answer by @yordansoares with its accompanying graphic.

Because if that is so, neither the CC nor the BCC fields work.

If this is inserted in the “Additional headers” setup field:

Reply-To: [your-email]
Bcc: [email protected]

…the form is still sent only to the recipient specified in the “To” field.

I’ve tried disabling all other plugins but this behaviour remains the case.

The only way I see to add another (single) recipient is to use the “Mail (2)” setup field—but that of course limits me to only one extra recipient.