Earlier today the proxy services were not available due to an outage. If you use any of the proxy services to connect to FastMail using your email client (such as smtp.proxy.fastmail.fm or imap.proxy.fastmail.fm) you may have been unable to connect. The web interface was still available.
The problem has now been resolved. The proxy services did not come back up correct during the reboot earlier today. We've put measures in place to ensure this problem will not return when another reboot is necessary.