Hi, Elena. :)
안녕하세요.
What he meant is that he is going to send it to you.
Technically it should be "부쳐줄게요" to be correct.
I understand students of Korean and even native speakers mix up those two words because
they are both quite similiar in pronunciation and they way they are spelt.
1."붙여줄게요" means
I am going to attach it for you.
I am going to paste it for you.
2. "부쳐줄게요" means
I am going to send it to you.(for you -in a Korean way of thinking)
I am going to mail it to you.
I am going to ship it to you.
So what he meant by that was " I am going to send it to you". He just spelt it wrong.
I hope this helps! =]