Service Desk currently allows to display image attachments embedded in the notification emails that are being sent from Service Desk.
Non-image files however can not get embedded.
In these cases, a customer is required to have access to the portal in order to fetch the files in question.
In certain situations, it will not be possible for customers to reach the portal, and all Service Desk functionality will go through email instead.
This can happen both when the customers environment does not allow access to outside networks, or if the network where JIRA Service Desk is hosted does not allow incoming traffic from outside the network.
File attachments on mail servers often are subject to a size restriction. If there is a mismatch between the size that Service Desk allows to get attached, and the mail server allows to process, there could surface some issues