Is it possible to create a trigger for particular emails? For example, every time we receive an email from customer.service@ups.com to be automatically assigned to a particular assignee (ops)?
You can use triggers to assign tickets to specific groups or agents based on the received at email. But you cannot specify a customer's email in that way. But there are workarounds.
You can create a specific support address in Zendesk under Admin>Channels>Email. Create a new support address there and it will be available as a trigger condition Received At>NewSupportaddress@MyZendesk.com. Then use an action to assign to a group or agent.
Or, you can use organisations so that every ticket from @ups.com is automatically directed to a specific support group.
Or, you can tag a user or an organisation. When a user creates a ticket, these tags will be added to the ticket. You can then use that tag in a trigger condition.
Tags>Contains at least one of the following> Trigger_to_XXX