There is not an option for this. Users need to have an account to open issues. They can be automatically added as @Alex Christensen indicates. If they only ever use email for opening/commenting on issues then not login required but if they use the portal then they need to login.
If you spend enough time as a Jira admin - whether you are managing a single, mid-sized instance, a large enterprise one or juggling multiple instances at once - you will eventually find yourself in ...
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG
You're one step closer to meeting fellow Atlassian users at your local meet up. Learn more about AUGs
We're bringing product updates and pro tips on teamwork to ten cities around the world.Save your spot