Hello,
I am trying to use the single send transactional send (POST request), but no matter what mail addreses I try I get this error when checking the send’s status:
"sendResult":"INVALID_TO_ADDRESS"
Please advise
Hey @EStoller 
. Great question. In my experience, this is typically a result of using a temporary or throw-away domain.
Are the addresses you are working with temporary-type domains?
Thanks! – Jaycee
Hi @Jaycee_Lewis,
Actually the problem was the other “to” fields - ‘cc’ and ‘bcc’, not the legitimate address in the “to” field. They were populated with an example array that didn’t contain a proper email. Something like [“string”]. Removing those fields/populating them with proper emails solved the problem.
Big thanks to Tom from support that helped me with that one.