I have a hotmail account. I have had my iPhone 4s for 2 years. My email was working fine until couple weeks ago. I don't know why or what has changed but now when I delete my messages using my phone, it does not delete them from my email account

I have a hotmail account. I have had my iPhone 4s for 2 years. My email was working fine until couple weeks ago. I don't know why or what has changed but now when I delete my messages using my phone, it does not delete them from my email account so when I log into my computer I still have a ton of emails in my inbox. Why is it doing this??

I have tried deleting and adding the email account back into my iphone. I have powered my iphone off and on - several times. Nothing works