Festal.
The Creator of our souls and bodies has given His bounty to both, and at one and the same time has overwhelmed us with good things that both heart and senses can feel. At the time of the sacred feast He has given us the rain we so much longed for, that our celebration might be clear of sadness. We have praised our bountiful Lord, and now as we are wont write a festal letter and address your piety with the request that you will aid us with your prayers.
Source: Letters (New Advent)