This will depend on two things:
1) the status of your Upgrade Protection
2) the version you are currently running. If your Upgrade Protection
is current and you are presently running VisNetic MailServer 6x, your 6x
license key will work in version 7x.
If your Upgrade Protection is current and you are presently running
VisNetic MailServer 5x, your 5x license key will not work in version 7x. You
must retrieve a new 7x
key. If your Upgrade Protection has expired, your existing license key
(regardless of version number) will not work in VisNetic MailServer 7x. You
your existing license.