Any employer can absorb you without relieving letter. However you may get it in writing from next employer that Relieving letter is not required.
However you should demand it in writing and get it as many employers in future may demand it................alongwith acknowledgment and acceptance of resignation, service certificate, Correct FnF statement (showing computation of earned wages,leave encashment,bonus etc, adjustment of correct notice pay at correct rate of notice pay for correct notice period), Form16 as per correct FnF statement, salary slips of all months,PF number and a/c slips of each year,ESIC card, NOC/NDC etc.......
All of these docs may serve as good as relieving letter.
Relieving letter is more of a practice than a legal requirement....................and signifies nothing but that there is nothing due towards employee.
Service Certificate has to be supplied to all employees.
What was the notice period stated in appointment letter issued to you?
Did you sign any service agreement/Bond?
You may go thru many threads on similar queries e.g.;
https://www.lawyersclubindia.com/forum/Non-issuance-of-relieving-letter-117843.asp#.VQVo8TKqqko