連絡先 and 宛先: contact information and a message’s recipient
Compare entering or exchanging contact information with addressing an envelope or checking an email recipient. Read a contact route separately from the destination of a particular message.
Information entered or exchanged for contact
連絡先 (れんらくさき) means contact information. 「申込書に住所と連絡先を記入した。」 means “I entered my address and contact information on the application.” The sentence reports entering an address and contact information on the application. It does not specify a particular phone number.
「旅行前に互いの緊急連絡先を交換した。」 means “We exchanged emergency contacts before the trip.” The people exchanged information for contacting each other before the trip. This is an exchange of contacts, not a report of action taken during an emergency.
The destination of a letter or message
宛先 (あてさき) means destination or address. 「封筒の表に宛先を大きく書いた。」 means “I wrote the destination address in large letters on the front of the envelope.” The address is the destination of that envelope. Writing it in large letters is a different action from the letter reaching its recipient.
「メールの宛先を間違えないよう送信前に確認した。」 means “I checked the recipient's email address before sending the message to avoid a mistake.” Here the destination is an email recipient, so 宛先 is not limited to postal addresses. The address was checked before sending to avoid a mistake.
Contact routes and particular destinations
連絡先 concerns information through which contact can be made. 宛先 concerns where a particular letter or message is directed. The same information can serve both relationships while having a different role in each sentence.
Exchanging emergency contacts focuses on ways to reach each other. Checking the email address focuses on that message’s destination. This difference is not determined only by whether the medium is a phone or postal mail.
How do emergency 連絡先 exchanged before a trip and an email 宛先 checked before sending differ in the role of the information?
Show the answer and why
The emergency contacts provide information for reaching each other. The email address identifies the destination of a particular message. Distinguish the contact route from the sending destination without turning the prior check into completed delivery.