Summary

When a user sends an email to a mail handler with an eml file as an attachment, and if the name of the attachment has a special character, the attachment gets renamed and loses eml format.

This causes inconvenience when trying to view the attachment in it's original format (email which is to be opened via email client)

Steps to Reproduce

1. A ticket is created in project A
2. A mail handler is responsible of adding comments to this ticket
3. An email is sent with the ticket key in the subject and an *.eml file attached.
4. Comment is added along with another comment from Jira mentioning "Renamed attached file: ... because it contained invalid character(s)."

Expected Results

Jira automatically renames the file attached from "Placehoder: Something.eml" to "Placeholder_ Something.eml" - Formatting should be kept, becuase this way the file can still be downloaded and opened as an email

Actual Results

Jira automatically renames the file attached from "Placehoder: Something.eml" to "Placeholder_ Something" - Formatting lost, cannot be opened as an email if downloaded.

Workaround

1. Download and save the file without an extension
2. Rename the file with the proper extension
3. Open it with preferred email client