General

Actually, it will be a really long answer. But the following picture (found on the internet, and the credit goes to it's original creator) will answer your question.

As of now (2020/04/14): @ce.pdn.ac.lk will be deleted one year after the graduation.
@eng.pdn.ac.lk will not be deleted in the foreseeable future.

Account	Username	Password
https://feels.pdn.ac.lk/	eXXYYY	Given to you during faculty orientation
CO Top floor lab linux computers, tesla, aiken, babbage, [at]ce.pdn.ac.lk email, results.ce.pdn.ac.lk	eXXYYY	Given to you during the department orientation
CO Top floor windows password	eXXYYY	Given on the first day of using windows software for a lab after enrolling in the department
CC windows password	eXXYYY	Given on the first day of using windows software for a lab after enrolling in the department
[at]eng.pdn.ac.lk password	You choose	You choose

Account	Whom to ask
https://feels.pdn.ac.lk/	'Lost Password' option on the login page
CO Top floor lab linux computers, tesla, aiken, babbage, [at]ce.pdn.ac.lk email, results.ce.pdn.ac.lk	Umega Rathnayake
CO Top floor windows password	Bandara Wasundara
CC windows password	Umega Rathnayake