What does in the mail mean

A common idiomatic expression!

"In the mail" is a phrase that means "on the way" or "arriving soon". It is often used to refer to something that is being sent or delivered through the postal service, such as a letter, package, or parcel.

For example:

In a broader sense, "in the mail" can also be used to refer to something that is being sent or delivered in a more general sense, such as:

Overall, "in the mail" is a convenient way to express that something is on its way or being delivered, without having to specify the exact method of delivery.