郵便
ゆうびん · yuubin · JLPT N3 · noun
postal service
📮✉️ 郵 relay post + 便 delivery service; yuubin sounds like you've been mailed
郵 first meant a courier relay station on the old post roads. 便 means convenience or a delivery run, as in 航空便 (airmail). Put together, the relay-station delivery is the postal service. For the sound: yuubin, you've been sent mail.
便 — person 亻 + change 更
A semantic compound: 亻(person) beside 更 (to change/replace). The original sense was a person making things easier or more convenient by adjusting them. From 'convenient' it extended to 'then/thereupon' (biàn) and to bodily 'discharge' (as in 大便).