This does not apply to anyone who is paying for our services.
Starting December 11, 2008, we are going to experiment with relaxing the over-limit action for free accounts. Instead of rejecting when a Basic account is over the free limit, messages will get a "try again later" defer response. This allows these messages to be throttled (it's still a free account, after all) to reduce the usage impact. Free accounts do cost us money to provide, and we need to limit the impact they have on our service in order to keep providing them.
The 48-hour cooling off period still applies. If you are using a free account don't like being without mail for 48 hours when you hit the limit, you should upgrade to a Personal level account.
This is not a policy change; we still reserve the right to change back to the official "reject" policy.