Routine emails “New Estimate Created” and “New Invoice Raised” add the option to include @EstimateName@ / @InvoiceName@ within the subject line.
When sending customers an email advice of estimate / invoice has been issued the subject line only allows for inclusion of estimate / invoice number but having the facility to include the “name” allows for easier reading by the recipients.
I suggest this Feature Request as a way to make communications more comprehensible at first glance i.e. subject line includes more than a number!