As was pointed out in this thread numerous times before, not only passwords, but the leaked email(s) itself should be replaced everywhere.
Domain theft is a major problem. Your email, be it account email @ another registrar or domain whois mail with or without whois privacy, is the first step to locate the victim (account, domains, security questions) and/or to start hacking work. Saying nothing about extra info, such as epik-regged domains you transferred away before. Even if your are still the only person accessing your email (different passwords used for epik and for email) - do yourself a favor and change the email.
Are security questions/answers required by a registrar or marketplace? Favorite color? Use random answers (different in each case).
Use different emails for each critical service. Have a lot of domains with "Registrar X" (not Epik?)? Start using an unique email with them, do not enter this email anywhere else, use it for communications with this registrar only.
I do not own sex .com or other million dollar domains - but in my domaining career I still saw
extremely sophisticated attempts to access my accounts, obtain PII including possible answers to security questions using social engineering, etc, etc.
Is your epik leaked email also snapnames/namejet/dropcatch whois email, or account email? Replace it. Do not forget to visit netsol, mydomain, bigrock. moniker, register .com and all other registrars you have an account with (as a result of snapnames-namejet old purchases). Replace account emails with them as well. Those accounts are permanently linked to snapnames or namejet. Sometimes, all existing domains with then be locked for 60 days (definitely the case @ netsol) - let it so be. NetSol now has a new interface, where the "billing" domain contact is almost invisible. Check billing contact email using an "old" link:
https://www.networksolutions.com/manage-it/billing-info.jsp , as you will possibly need to update email at this section separately.
Be paranoid. It would not harm.