just saw that epel has been moved to archives lately.
Most repo will go this way.
We have worked to let at least our repo available even for obsolete release. Since SME 8 mirror repo should point to the obsolete locationto at least help you to update the SME before migration.
Also, while buggy and needing a manual intervention smeserver-yum now should let you get updates from the vault.centos.org also to help you update to last version before migrating.
If you really need to keep your server running for a while then you might consider buying an extended support from red hat for rhel6. I have no interest in you doing so.
Lastly, we do not intend offering ourself an extended support, but that being said as SME 10 is not out we will release today sudo CVE fix.