Who's running my email account?

Hi

I am a new switcher from PC to iMac at Christmas. On the PC I had everything set up to run as I wanted it to, and without thinking. Now that I am moving over I am having trouble with my email account. This maybe a little silly but I am not sure who is running my email account? I have my own domain name www.huttriverprovince.net which is the email address that I use. My problem is that I can not remember the passwords to put into the iMac, and I am not sure who I should contact to reset them??

I know this is not your normal request, but with everything just set up before I am not sure who to ask, I know my ISP is BT in the UK, but I have not idea who to contact to rest the passwords for the email address.

Luckily I have all my emails copied to my hotmail account which is how I am getting them at the moment but I would like to get them on the iMac soon. Any tips?

Pete