An Owl would fly into the office for the Headmaster of Hogwarts. The letter listing as being from Level 4 of the Ministry of Magic. The name and address on the letter is, unusually poorly written for someone in the ministry. The name and address clearly reading. "Knox Greyfriar. Head of Hogwarts." However it is written in a basic way, as if the writer had used stencils or were guided on how to write each letter separately instead of writing as actual words. With the letter opened it was even worse, very few of the words were eligible with the only few ones being the same as on the front and the last being "Marida", if anything could be read from the child like scribbling, words would be written down as you would pronounce making it harder to read.

Shortly after the first letter a second would follow and land. Written much more neatly and not by a child. This letter is also from Level 4 and reads the same on the front with a good cursive form, inside the letter read.

Dear Mr Greyfriar.
Wizengamot Elder
Headmaster of Hogwarts.

Dear Greyfriar. I write for Marida, Centaur Representative in the Centaur Liaison office, Level 4 of the Ministry of Magic. Regulation and Control of Magical Creatures.
Please disregard the previous letter, it came to my attention Marida had sent it without informing anyone of her intentions.
Marida has expressed interest in visiting Hogwarts School of Witchcraft and Wizadry, namely the grounds along with the Forbidden Forest to meet the colony of Centaurs living there.

In return Marida has offered to lend her services to the school or to you as a form of compensation and is willing to bargain for the opportunity.

We wish to hear from you soon with your offer.

Sincerely
Marida's writer

Slipped into the letter is a poorly written like the first letter, but still readable address, saying to send the reply to the Schlagenweit Estate as if trying to bypass the Ministry.

Upon seeing a letter from the Department for the Regulation and Control of Magical Creatures, Knox's heart began to race. It was only days after the full moon and horrors revealed the next morning.  He snapped open the envelope. He might have thought it an illegible joke for all he could do with it. When the next owl arrived, he took it as a sign and found both something readable and a relief.

Hogwarts business. Not another disaster or another warning. Just ... Hogwarts business. And intersting, hopeful business at that. When he saw the addendum with the retrun address of the Schlagenweit Estate he paused. Well, he told himself, it was past time being surprised at the life and times of Sasha Schlagenweit.

He immediately penned a reply, and opened with his best Centaur rune, one of a few he knew. It was a formal greeting.

15 Jan 2012

Marida,

I was pleased to receive your letters. It seems you went to some trouble to send them so I hope  my response will make the toil worth your while. While I acknowledge passage into Hogwarts grounds is granted me by witches and wizards' traditions, I humbly cede authority of the comings and goings concerning the local centaur herd to the centaurs. If they have welcomed you, then I do as well.

As it would be rude to entirely dismiss your offer of a return favor, I will not. I will however defer it indefinitely. No repayment is required for what I believe to be an ancient right afforded your kin to these woods.

I would be happy to welcome you to the grounds myself when you arrive, but if you'd prefer to avoid the awkwardness I will understand.

Cordially yours,

Knox T. Greyfriar
Hogwarts Headmaster

At the end of the day, with all the work from having to fly from London, to Scotland, then back again. Travelling the entire length and more of the United Kingdom in a day the poor owl dropped its letter and then rested, worn out and shattered from its flight and needing a well earned rest.

The letter it dropped off would be neatly written again, although some attempts had been made to get more writing on it. But it seems whoever is writing for the centaur had won in the end despite their efforts.

Dear Mr Greyfriar.
Wizengamot Elder
Headmaster of Hogwarts.

Mr Greyfriar, Marida is very pleased with the response and is looking forwards to the opportunity to meet the colony.
She has said she would be ecstatic to meet someone as highly regarded and well known as yourself.
To this end she has asked for an available date along with the time. In addition the meeting place, be it the gates or in Hogsmeade.

She is excited to meet you.

Sincerely
Marida's writer.

There are some further marks on the letter that looks like attempts for Marida to try to write herself in instead of having another person write for her.