If you create a new issue with attachments, they will automatically upload in your Jira issue.
You can make any adjustment here and delete one, if you don´t need all of them. For delete one, you click on the attachment, and the blue hook disappears. If you don´t change anything, the attachments are all automatically uploaded.
Delete one without the hook, looks like this.
In your Jira for Outlook Settings you can also change the automatically upload of your attachments.
