What term is used to determine if an item can be admitted into the mailstream?

Mailability is the correct term used to determine if an item can be admitted into the mailstream. This concept encompasses various factors such as the item's size, weight, shape, and contents, to evaluate whether it meets postal regulations and standards for mailing. Understanding mailability is crucial for ensuring that items can be processed by postal services without issues, thus allowing them to be delivered to recipients as intended.

Acceptability, while similar in meaning, generally refers to whether a product or service meets specific criteria or standards but does not focus specifically on postal regulations like mailability does. Eligibility usually pertains to whether an item or person qualifies for a specific program or service, such as discounts or special mailing rates, rather than the ability to be mailed in the first place. Transportability relates to the logistics of moving an item from one location to another but does not directly address the criteria set by mail services regarding what can be mailed.