This is the 15600th most frequent Korean word.
보낸다고
"보낸다고" means "(saying that someone) sends" or "(saying that someone) will send."
In this sentence, '보낸다고' indicates reported speech, communicating what someone said regarding sending a letter.
그는 나에게 편지를 보낸다고 했다.
He said he would send me a letter.
Here, '보낸다고' represents an action the speaker thought they were performing, which in this case is sending a message.
친구한테 메시지를 보낸다고 생각했는데 보내지 못했어요.
I thought I was sending a message to a friend, but I couldn't send it.
The usage of '보낸다고' in this sentence suggests a promise or intention to perform the action of sending an email.