The link between a Department and an email account is made using built-in  Triggers.

Linking Email Accounts to Departments

Each email account has a New Ticket Trigger which assigns Tickets submitted to that email account to a specified Department. For example, you could have all Tickets created by emailing support@yourcompany.com assigned to the Support Department.

You can view and edit the Trigger by going to Tickets > Email Accounts and selecting the relevant email account.

You can also view and edit these Triggers for each email account in Email Account Triggers under Tickets > Triggers > New Ticket.

Linking non-email Tickets to email accounts

The New Ticket Trigger in a Department’s properties screen sets the email account to use for Tickets not submitted through email - for example, via the Portal an embedded form, or the API - in that Department. The selected account will be used to send messages related to the Ticket. For example, a Ticket submitted to the Support Department via the web would have its emails sent fromsupport@yourcompany.com.

You can also view and edit these Triggers for each Department in Department Triggers under Tickets > Triggers > New Ticket or Ticket Update or New Reply

The Ticket Changed Trigger sets the email account when an existing Ticket is changed to the Department.