We can also send our friends message by e-mails.=We can also send __ __our friends by e-mails.

问题描述:

We can also send our friends message by e-mails.=We can also send __ __our friends by e-mails.

message to

We can also send our friends message by e-mails.=We can also send (message to) our friends by e-mails.