Colloquial term for a mail carrier; often used with the honorific さん as 郵便屋さん. More casual than 郵便配達員.
The mail carrier delivered the letter.
毎朝、郵便屋さんが来るのを楽しみにしている。
I look forward to the mail carrier coming every morning.
The mailman delivered the package for me.
The mailman comes around 10 a.m. every morning.