Normally in Vanilla Skyrim, you can't use horses on Solstheim. However some mods like Convenient Horses or Immersive Horses let you use horses there.
Or when you use Arvak, you might face a similar problem.
When you try to exit Raven Rock through the south exit, you could get stuck, while on horseback, because the the ceiling is quite low. With this tweak, you should be able to leave Raven Rock on horseback.

This mod doesn't require any horse mods as hard requirement. However, to be able to use horses on Solstheim, you need to use one. (Unless you summon Arvak.)

This mod does require the Dragonborn DLC. (obviously!)

Credit

- AjiraKimberly - For pointing this issue out on his livestream
- Bethesda - For Skyrim
- The whole modding community - for being awesome! <3

Permissions

- You can alter/expand/use this mod as you like, as long as you don't use it for any paid mod projects.