All tickets containing certain keywords or properties can be assigned to an agent group using Freshdesk Automations. To set this up, go to Admin > Workflows > Automations > Ticket creation>New rule and you can set something like this-
Feel free to drop a note here incase of further assistance :)
The above Automation works for sure. There is also an easier way.
Inside the email settings (Admin->Emails->Click on the pencil icon right next to the concerned email address), You can directly assign the tickets to the group that you want: