Details
Description
A Universally Unique ID is being created for each attachment for the message.
If in case MIME Spec doesn't restrict to have an universally unique id, a sequential counter can be used to provide unique identifiers for different attachments in a message.
Or we can create a single UUID for a message and can reuse the UUID by appending a counter to it for each attachment.
This will save a substaintial time as UUID.randomUUID() is a very heavy call.