Domanassa: Mental Pain
Domanassa is pain that belongs to the mind rather than the body. No one had thrown a punch when that letter was begun, yet the affliction squeezed like a fist under the ribs, which is how mental pain works: it borrows the body's language without needing a blow. Writing hard words to people you love costs the writer first, and that cost is spent on the page before any accusation lands.
Karuṇā: Compassion
Karuṇā is the heart's shaking when someone else is in trouble. Tears fell on that letter because the damage the Corinthian quarrel was doing to them was already visible, and seeing it plainly is what wrings water from the eyes. The wrong done to the writer takes up no space here; the ache is entirely for the people receiving it. Compassion of this kind runs ahead of the event, the way a parent flinches watching a child run toward the road.
Codanā: Reproof
Codanā is the act of naming another's fault to their face. Reproof is permitted only from someone speaking at the right time, in truth, gently, for benefit, and with goodwill in mind, and tears on the page are the evidence for that last condition. An earlier letter had already gone out sharp, and what comes now is an account of the state the writer was in while sending it. Pointing out a fault is easy; arriving at it in sorrow instead of satisfaction is the hard part.
Mettā: Loving-kindness
Mettā is steady goodwill toward another person. Abundance is its ordinary sign: goodwill does not run dry when someone disappoints you, the way a well keeps filling after you have drawn from it. The letter went out not to leave anyone in grief but to make that goodwill visible, since love that stays quiet about a fault can be mistaken for indifference.
Kalyāṇamitta: Good Friend
Kalyāṇamitta is the friend whose company moves you toward what is wholesome. Such a friend is the one who will tell you the unwelcome thing, and a letter written in tears from across the sea is that duty carried out at a distance. Waiting afterward for news of how it landed belongs to the friendship as much as the writing did.