If you see this error when trying to delete a request type, it means that the email channel for your service desk uses this request type as the default one for all the requests coming from emails. When JIRA Service Desk pulls emails from the associated email account and creates requests, this request type is assigned to the requests automatically.
解決方法：
JIRA administrators can change the default request type for email requests to be another one by going to Settings > Email settings in your service desk. For more information about the email channel setup, see Setting up the email channel.
When JIRA Service Desk creates new requests from emails sent to the email account associated with your service desk, it copies the email subject to the Summary field and the email content to the Description field. When more fields are required, JIRA Service Desk cannot parse emails to fill them in with correct values.
解決方法：
次のオプションがあります。
非表示フィールドを表示したい場合は、オプションフィールドにします。
Ask your JIRA administrator to change the default request type for the email channel to use a different request type, and then modify your request type to include more required fields. You can also create a new request type for the email channel if no existing types are suitable. For more information about the email channel setup, see Setting up the email channel.
