Unfortunately, any mail you sent overnight or this morning may have been lost. (You should have gotten a bounce message, but those have become essentially useless thanks to the dozens to thousands of bounce messages most of us get due to forged virus and spam e-mails, and of course it's possible that the bounces bounced.)
Also, any mail sent to you overnight or this morning may have been lost. (Again, the sender should have gotten a bounce message, but they may never notice it, or the bounce could have bounced, and you won't know they tried to reach you. Automated senders in particular will probably never know that their mail didn't reach you, and list servers such as yahoogroups.com will probably decide you no longer exist, and unsubscribe you.)
If you sent any messages, it wouldn't be a bad idea to resend them just in case. If you were expecting anything, it couldn't hurt to ask the sender to resend. If you're subscribed to any mailing lists, I'd suggest checking your subscription status.
We regret the inconvenience.