Reply from wrong address

[#1]

I have a domain name email with plusnet.
If I reply to a message which is a reply to my original domain email, It sends it from my "plus.com" email address (Windows Live) and not my personal domain address that i used in the original email.
I know i can change the address to what email account i want to send in the drop down on windows live but that seems to often go into peoples spam folder.
Can i set things up so that if i send from  samtech @ blah.co.uk  then reply to my reply, that it automatically goes from samtech @ blah.co.uk again and not my plus.com address?

[#2]

If you set up the Windows Live Mail account using your domain address instead of your Plusnet address I would expect it to behave as you require. If you need to check, set up instructions for Windows Live Mail can be found in the Help pages here.
Was the email account giving trouble set up that way?

[#3]

Ok i set up Windows Live with removing my 2 plusnet email addresses but couldn't receive any mail to my domain email address.
I've also lost all my mail to my domain address inbox as it must have come through my plusnet address.
I have now set it up as it was and i'm receiving mail again but can i get my lost messages back?
Seems i need my plusnet address to be able to get mail to my domain address.
Is there a number i can call to help sort this problem?

[#4]

I found the tech number and they resolved my problem.
Thanks for the help.