Steps to reproduce:

1. Create a mail handler that creates Issues of Issue Type X in a specific project, as in:
   • "Create a new issue or add a comment to an existing issue"
   • "Create a new issue from each email message"
2. Remove issue type X from the project's issue type scheme

Expected result:

The creation of issues from the mail handler will fail due to the issue type being invalid.

Actual result:

The issue is created as issue type X

Notes

It was observed that this problem may cause strange behaviors on filters like the Open Issues filter.

Workaround

Edit the mail handler or the issue type scheme being used by the project mapping the missing issue type.