Mailing attn

You're referring to "Attn" as a shorthand for "Attention"!

When writing a mailing address, "Attn" is often used to get the attention of a specific person or department within an organization. Here's the correct format:

Attn: [Name] [Organization] [Address] [City, State ZIP Code]

For example:

Attn: John Smith ABC Corporation 123 Main Street Anytown, CA 12345

Using "Attn" helps ensure that your mail or package is delivered to the correct person or department within the organization.