The first step is to try to recover the email address through the provider:
Can't access email
. If that doesn't work, then your best bet would be to change the email address on the account by forcibly removing the inaccessible registered email address on those accounts:
Change registered email
. You have to recover the account in question by proving that you own it.
At the beginning of the process, they ask you for an email address. Make sure that you select a Google Mail address as those have proven to show the least amount of issues for RuneScape players. If you need help recovering your account, you should head here:
Account recovery denied
.
Once you
successfully
recover the account, the old, inaccessible email address will be automatically replaced by the new email address that you have chosen at the beginning of account recovery procedure.