Page is working in local but on server page is not working

Question

Hello Everyone

     I am working on hrms project in that when employee want to leave that time mail will goes to the hr .that all code run perfectly in local but when i will upload on server the mail functionality not working.

I was use smtp for mail.

if i run without mail funtionality then it will work on server bt with mail funtionality it will not work.

I thing its server issue

how can i solve this issue..?

i hope anyone give me solution