What does 'upset me greatly' mean here? ?

Question

I sent the following message out to people who previously attended a trip that was affiliated with a charity after I made a complaint to the regulator about the charity. 

"Hi,

Please see attached statement and covering letter which has been sent to the Regulator regarding the Charity. I am sending a these to anyone who they may be of interest to.  

Kind Regards,

[My Name]

One got back, saying:

"This does not interest me, it upsets me greatly..."

What does 'upsets me greatly' mean here - are they saying the contents of my complaint upset them, or the fact that I complained in the first place? 

Answer 1

I'm thinking that the fact that you made a complaint is what has upset this person.

Answer 2

It's not clear. They could have been more specific. Since they start by saying "this does not interest me", I would guess that it's your letter than upsets them. But there's no way to really know.