Entourage, Outlook, and multiple computers

A brief entry by way of illustrating a hazard I hadn’t heretofore considered.

My client uses Microsoft Outlook 2004 11.4.1 on OS X 10.4.11, connected to a corporate Exchange server. She subscribes to several mailing lists. Recently, she began seeing repeat deliveries of mailing list messages she removed from her inbox.

We tried forcing a server sync, rebuilding the database, recreating the Entourage account, and eventually an entirely new identity in Entourage. More annoyingly, it wasn’t happening with non-list messages. Frustrated, I passed the cases to the system admins, who had previously handed it to me with a single casenote: “Does not appear to be a server problem.”

Thank you for your attention to detail.

I passed it back with an explanation of what I’d done to troubleshoot, and a request that they examine several messages more closely. I also asked that in the event they came to the same conclusion again, they document their reasoning and troubleshooting steps.

The next day, I repossessed the case, and documented the solution.

In an offhand conversation unrelated to the case, the client has asked if I would look at her personal computer, which had been running progressively more slowly. After some questions designed to draw out preliminary solutions, she mentioned that she never restarts the computer, or even logs out. I asked her if she left her home installation of Entourage running all day long as well.

Nailed it in one.

She was deleting the messages at work, emptying the Deleted Items, and allowing the client to synchronize to the server. A few minutes later, the server would hear from the home machine, which would report the messages not deleted, and return them from the dead — so to speak. Then the office machine would contact the server again, see the messages in the database, and redisplay them. Et, as they say, voila! Instant reappearing mail.

Why only mail list messages? I don’t know, but I don’t think it was just mail list messages. I think that because she removed so many of them, and because the reappearances were so very obvious, that they just stuck out more.

Moral of the story: Allowing two copies of Entourage to modify the mail database simultaneously is bad juju. That much seems obvious on the face of it, but having never seen the symptoms, I stumbled on the cause by sheer luck.