送る and 送信: the sent object and information transmission
Compare sending a package or accompanying a person with transmitting information such as email. Read the object, destination, and checking-before-sending order.
Send a package with 送る
送る, read おくる, means send or see off. 遠くの友人に小包を送った。 says that someone sent a package to a friend far away.
小包 is the sent object and 友人 the recipient. Read both without restricting 送る to information transmission.
Check the contents and then send the email
送信, read そうしん, means send or transmit. 内容を確認してからメールを送信した。 says that someone checked the contents and then sent the email.
Both checking and sending are reported, with 確認してから giving their order. Preserve the completed transmission rather than reducing it to preparation alone.
Accompany a person and read transmission time
駅まで客を送ってから家へ戻った。 says that someone accompanied the guest to the station and then returned home. Read the person, the endpoint at the station, and the return order.
電波が弱く、写真の送信に時間がかかった。 says that sending the photo took time because the signal was weak. Read the cause of the delay without adding an unstated transmission failure.
What action order is supplied by 内容を確認してからメールを送信した。?
Show the answer and why
The contents were checked and then the email was sent. Preserve both completed actions and their order rather than reducing the scene to checking alone.