email account problem

Dear all,

I have iphone 4 on which I added 3 email accounts, 2 hotmail and one exchange and it was working properly. Suddenly, one of the hotmail accounts started working in a strange way that whenever I try to access that account suddenly the email application dim and the phone return to the main menue. I tried to restart my device but it did not work. Then I tried to delete the account and add it again unfortunately I faced the same problem. However, when I delet that account the email works fine with the other two accounts. Finally, I tried to add the same account on my firends iphone 4 and he faced the same problem so I was sure that there is a problem with that email account but the strange thing is that it was workng fine before 2 days and I did not change anything with my device. I tried also to change the password of that email account but also I faced the same problme.

Please if you have any suggestions or solutions let me know cause I want that emil account to be with me all the time.

Note, I did a trick that I forwarded that email account to the working one but I want to know what is the reason behind this issue fi anyone face it before.

waiting your responses ASAP.

thanks in advance