Sorry for the problems.. let me explain what's going on!
As a first step towards being able to let users log in as firstname.lastname@example.org instead of just m#######, we're changing the way our alias system works a bit.
Basically, starting last night, there is now a 1to1 mapping between mailboxes and email addresses. This is so when somebody logs in as email@example.com in the future, we can figure out immediately exactly which mailbox they meant. Fortunately, although this seems like a restriction of features, it won't actually result in any less functionality, because email addresses can still forward to multiple email addresses (even though they can only go to at most one DreamHost mailbox).
So, let's say before you had firstname.lastname@example.org and email@example.com both going to mailbox m123. Now, firstname.lastname@example.org will still go to m123, but email@example.com will just forward to firstname.lastname@example.org. Everything still works the same, but now we know that m123 <=> email@example.com.
To go with this change, and in preparation for the new firstname.lastname@example.org paradigm, there's that new Addresses tab in our web panel, and no more old Mailboxes tab. Also, we're running a script right now that's going through all hundreds of thousands of aliases and mailboxes and smartily redoing the maps like in the example above!
That's where the little problems are you're talking about are coming up.. I didn't realize it would take over 48 hours for this script to complete (it should be done by tomorrow around 5pm Pacific)! So for a little while, some people aren't seeing the mailbox that their email addresses are tied to.
I planned to do the switch to the new tab right as the script switched all the data over, but that's kinda hard when the script runs for two days! So it was decided to do the switch of the panel first.. or else we'd have to re-run the script afterwards because more users would be set up incorrectly during the running.
At this point, I think most of your users actually should be switched over (it's working from most recent to oldest).. so please check out the panel again and see if things still make no sense! If they're still messed up, if possible try waiting until Wednesday morning and check again.. if they're still messed up then, something is definitely awry.. please contact email@example.com about it!
Also, about the mailbox rotation, I had thought we'd actually already made that required, but it looks like not! I'll see about switching it back..
Hope this all makes sense and I really appreciate your understanding during the transition!