1
push sth through the letterbox
此处letterbox指门上的投信口。
She pushed the card through the letterbox.
她把卡片从投信口塞了进去。
邮筒
先理解核心含义，再看它在真实句子里的用法。
邮筒
A public box in the street for posting letters.
She pushed the card through the letterbox.
她把卡片从投信口塞了进去。
一种通过线索寻找的隐藏容器,内装日志和橡皮图章,供娱乐之用。
A hidden container that holds a logbook and rubber stamp, found by following clues as a form of recreation.
长方形孔洞或缝隙。
A rectangular hole or slot.
I found a parcel inside the letterbox this morning.
我今天早上在信箱里发现了一个包裹。
The letterbox in the front door makes it easy to receive mail.
前门上的投信口使收信变得很方便。
There are two red letterboxes near the station.
车站附近有两个红色的邮筒。
此处letterbox指门上的投信口。
She pushed the card through the letterbox.
她把卡片从投信口塞了进去。
用full of表示“满是……”，letterbox指收取信件的信箱。
The letterbox is full of post.
信箱里堆满了邮件。
这里letterbox指用于寄信的邮筒。
There is a letterbox outside the post office.
邮局外面有一个邮筒。
Not this
I dropped the letter into letterbox.
Use this
I dropped the letter into a letterbox.
汉语没有冠词；letterbox 是可数名词，单数前需加 a/the。a letterbox 表示“一个邮筒/信箱”，所以这里要加 a。
Not this
I have many unread emails in my letterbox.
Use this
I have many unread emails in my inbox.
letterbox 指实物的邮筒、信箱或门上的投信口，不指电子邮箱。汉语“信箱”可兼指实物和电子邮箱，但英语中电子邮件收在 inbox 里，用 inbox 才正确。
Not this
The postman pushed the envelope into the door letterbox.
Use this
The postman pushed the envelope through the door letterbox.
door letterbox 是门上的窄缝，信笺是穿过（through）它进入屋内，而不是停在缝隙里，所以介词应用 through。汉语“投进去”的“进”易导致误用 into。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
把信投进邮筒
I dropped a letter in the letterbox on my way to work.
我在上班途中把信投进了邮筒。
从投信口（塞进/递进）
The postman pushed the envelope through the letterbox.
邮递员把信封从投信口塞了进去。
投信口盖
He painted the letterbox flap red.
他把投信口盖漆成了红色。
查看邮箱/信箱
Could you check the letterbox for mail?
你能看一下邮箱里有没有邮件吗？
公用信箱
The communal letterboxes in our building are locked.
我们楼里的公用信箱是上锁的。
Use letterbox naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
把 letter(信)和 box(箱)拼在一起：装信的小箱子，就是邮筒/投信口。
语域：mixed 常见场景：residential mail delivery、public postal drop-off 该词作名词时的语域较中性，通常用于日常收信或寄信场景；在英式英语中多指住宅的投信口或信箱，在美式英语中则常换用其他说法。语域会因地区和具体使用场合而有变化，一般不特别正式或非正式。
Words ending in -box (/bɑːks/) rhyme with letterbox: box, mailbox, sandbox, soapbox, pillbox. Note that letter (/ˈlɛtər/) shares the initial spelling and sound but does not rhyme with the whole word.
Dictionary facts from ECDICT, WIKTIONARY.