Problem Statement:

Email attachments containing special characters failed to upload on the ticket with the error: "Failed to add the following attachment to this issue because the file name is invalid." when sending email to the JSM mail handler.

Steps to Reproduce

1. Create or comment on a ticket via email with an attachment containing a special character like {' ', '/', '\"', ':', '?', '', '<', '|', '>'} by sending email to the JSM mail handler within the project. For eg. The filename is: "sys_attachment.do?sys_id=65ae4ef9976fa5101a7ab7afe153afad.JPG".

Result:
The attachment failed to upload with an error: "Failed to add the following attachment to this issue because the file name is invalid." and this is an expected behaviour for JSM mail handler.

However, if the same file is sent to a global mail handler then the file gets attached to the ticket as the global mail handler replaces the invalid character with "_" (underscore) as documented here .

Currently, the file validation process is a little different for JSM and the global Jira mail handler.

Suggestion:

JSM to implement the same file validation process of replacing the invalid character with an underscore or any other valid character as we have for the global Jira mail handler.