どうふう同封doufuu
1.
The act of placing additional items, such as photographs or documents, inside an envelope along with a letter.
2.
The process of including supplementary materials in a correspondence, signifying that they are part of the same communication.
3.
The practice of enclosing various items within a mailing, indicating an intention to share or provide more information to the recipient.
Example:
彼女は小切手を同封して私に送ってくれた。