In some scenarios you'll want to auto-assign a ticket to the first agent that responds to the ticket by email. You might e.g. have a trigger that email notifies all agents in a specific group, whenever a user submits a request for assistance. You would then want to assign the ticket to the first agent responding to the ticket notification via email.
You can easily set up a trigger accomplishing this behaviour. Name your trigger e.g. "Auto-assign to first email responding agent" and select the following conditions and actions:
Note, if you remove the "Via Is email" condition, the trigger will always assign to the first responding agent. Not just when the agent responds per email, but also when the agent updates a ticket online. This might be beneficial in some setups.
Zendesk accounts created after June 16th already have this trigger included, although inactive. Simply activate it to enable the auto-assign functionality.