One Character == World of Suck

Ladies and Gentlemen, today you are going to learn a lesson on why you do NOT edit the active directory directly for exchange attributes.

Background

A long time ago, we had a very crappy provisioning system for our hosted Exchange 2003 platform. It worked ok, but missed a lot of things that we wanted to have set. They also were kind of pricks when it came to licensing so making a ton of money on the platform was hard to do. So, we decided to roll our own. It wasn’t that hard to reverse engineer what was being set for users, groups and contacts. There were a few obstacles of coarse but we were able to get a pretty good provisioning system setup. However, this too had its faults. Sure we had total control over the code and could update things as we needed. But we were still working in a void. We really didn’t know _everything_ that was happening on the system that needed to actually happen. Plain and simple, we were missing things. Not to mention future services would require the same amount of dev time reverse engineering what needed to be set. That’s not a scalable solution.

So, when it came time to roll out our Exchange 2007 environment, we have moved over to HMC and for the most part, things have been a lot happier.

The Issue

Since we have this shiny new 2007 platform, we thought it was in our best interest to start migrating our users from the 2003 platform and away from the old clunky provisioning. So far we have moved some smaller customers and everything has gone pretty smooth. Certain customers have required the migration to happen in stages so we have come up with a decent solution to make this as smooth as possible. We define the list of users to migrate, setup a temporary domain on the 2003 platform, add smtp aliases to the users on the 2007 platform and then enable forwarding on the 2003 platform to the 2007 temporary smtp alias. All mail still flows as it did before, its just that some users happen to be on the 2007 platform getting their email. Easy as can be right?

Well, the users that we have moved so far have been fairly small customers. So the need for automating certain aspects of the move have been put off. There is a lot of automation that happens, but some of the tasks were put off such as the setting of the forwarding address.

That is, until last week. Last week we were starting to move one of the bigger customers so I setup a script that would take the users that were being moved and automatically set the forwarding address. Here is the code that I had in place to figure out the forwarding address:

            // need to add forwarding address here.
            list($tuname, $tdmn) = explode("@", $user['mail']);
            // new address
            $fwd = "{$tuname}@{$newdomain}\n";

Notice the $fwd variable. This is where the trouble begins. You can ignore the {} as those simply tell the parser that these are valid variables contained within the string.

No, the real issue is at the end of the line. Specifically, the \n. Technically, you can set the AD object to whatever you want. It will take this as a value. However, Exchange does not like this. With forwarding in exchange, you set the forwarding to an object. Typically another user, group of contact. Since we allow for users to forward to multiple people, we create a group automatically and populate that with one or more users, groups or contacts.

Now for the really bad part. I’m not sure if this is just Exchange 2003 or if others are affected as well. But when you forward to a group that contains a single contact object that has invalid characters, your email message with be lost in the ether. Gone, Kaput, Not even an NDR will be generated. We were unable to even find logs that the message came in it failed that spectacularly.

Conclusion

So the moral of the story is, don’t do what we did. Microsoft will tell you the exact same thing. Its dumb to do what we did. You should not be messing with the AD attributes directly in this instance. There is a certain level of error checking that must take place at the upper levels which were missed by both my script, and the provisioning system. But in the same breath, I can’t say for sure that HMC was mature enough to use when we first rolled out the 2003 platform. So whether it is you editing AD directly or someone else doing it, its just as bad. It just depends on how much control you want over the gun pointed at your head.

Matt Patterson avatar
About Matt Patterson
Husband, Father of 3, Programmer at heart, spends his days running ridiculously large data centers in the midwest.