Last night I had a bit of a panic when I deleted a user account (and the corresponding Exchange Server mailbox). Strictly speaking, deleting the user and associated mailbox was not a mistake – but I deleted the wrong one. Luckily, it’s a pretty easy mistake to rectify – as described in Microsoft knowledge base articles 274343 and 823176.
There is one thing that it might be useful to be aware of – even though I kept running the cleanup agent the tombstoned mailbox didn’t show as disconnected (so I couldn’t reconnect or purge); however, like so many things in Exchange, I left it for a few hours (actually, it was overnight but I’m sure a few hours would have been fine) before refreshing Exchange System Manager and everything was as expected (after which I simply reconnected the mailbox to a new Active Directory user account and logged in successfully).