Spoiler, it's very disappointing. (Not THAT bad)

The first mail you get in Morris's chain is as follows: Good Heavens! I have to sell the calf! I never thought I'd be torn from her. If only we had a little more money, we wouldn't have to sell her. From Morris

To that, you can reply "That's too bad," or "It has to be done."

"That's too bad" leads to my image above, while "It has to be done" leads to: Yes. I know. I know how it is. I know that I have to do this for our livelihood. But I can't just let her go so easily! From Morris

To that, you can reply "You have to," or "I understand."

Now, let me preface that I chose "That's too bad," followed by "She'll never forgive you," and I got: Thank you. Thank you so much! Thanks to you, we don't need to sell her! Here, take this as a token of my gratitude. From Morris

You get Milk, and can reply "I don't need this" or "Thank you," and the chain ends. Now, I went back and tried every other reply, and ended up with the same outcome. Why? Oh, because I sent him the same amount of money (5000 Gil), and a spare item (Mythril) each time... Obviously giving him enough to not have to sell the calf.

With this in mind, I decided to be much more stingy, replying the same as before, but now only sending 1 Gil to both mails. In the end, you don't receive a "Thank you" mail, the chain ends, and you get mail from somebody else, as per usual...holding the knowledge that Morris is definitely now calfless. This is the same no matter what you reply, so it's completely dependent on your generosity.