Status (by robm at Mon Jul 26 01:41 UTC)
Some users will experience a short outage when trying to access their email sometime over the next 30 minutes. The outage shouldn’t last more than 1-2 minutes. This is to roll out some new IMAP server code.
Update (by robm at Mon Jul 26 02:26 UTC)
The new code has been rolled out. The upgrade process caused a load spike larger than expected causing some problems accessing email for some people, but everything is returning back to normal now.