Many years ago I made a SEGA ID with the intention to use it to play JP PSO2. That never ended up happening so the account just sat empty and abandoned for years.
Recently, I got an email from SEGA and it reminded me that the account exists, so I set out to delete it.

I had problems with attaching images to this post so they have to be links, I'm sorry about that.
Since I can't read Japanese, I used a translator and intuition for the majority of my efforts.

I found an account deletion guide (https://fukoto.com/sega-id-delete-kuso2/). I followed it as closely as I could. I submitted an account deletion request ticket to SEGA and got this email back which started with: https://ibb.co/3yGcSx1 (#0)
I replied to the email following the template, giving my information, only to get a 553 Message filtered error in two separate attempts: https://ibb.co/SnKHsy3 (#1) https://ibb.co/6rZ8H33 (#2)

Is there something I'm doing wrong? Is it actually impossible to delete a SEGA ID? I'd really rather not have an unused account lying around.

Thank you for reading.