noun
Computing and telecommunications term for the entity that initiates a message, call, or data transmission.
メールの発信元を確認してください。
Please check the sender of the email.
このデータの発信元は不明です。
The source of this data is unknown.
Refers specifically to a person who sends a message, whereas 発信元 can be a person, device, or organization.
Compound of 発信 (transmission) and 元 (origin, source).