| Monday, June 4, 2007 |
16:23 - It's not stupid. It's advaaaaanced!
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Here's a neat party trick with which to amaze your friends.
I discovered that some of my notification e-mails were not getting through to my mail account on my work's Exchange server. I wasn't getting a bounce message either, though. The messages were just plain disappearing.
This was not, I repeat, not due to spam controls on the Exchange server, somehow determining that what I was sending was spam. During investigation, the IT guy and I dialed down the spam filters to allow pretty much anything through. And now, instead of reporting that the server had rejected the message as spam, Exchange was giving the helpful error "Advanced Queue failed to deliver message".
(Little is more charming than when software boasts and chokes at the same time.)
Yet it was apparently something to do with the content of the particular message I was trying to send, because other messages continued to get through just fine.
So I started b-tree searching. I'd trim down the message by piping it through head, then piping the output of that into mail. I started with 30 lines (out of about 200), then 60, then 100. At 150, the messages—which had been appearing almost immediately in my inbox after I'd sent them—stopped showing up. I cranked it back and approached from below, and found that it started gagging on line 116.
Line 116 had the following string in it:
consumptionjunction.com
Note: if you choose to interpret this string as a URL and put it in a web browser, the results are NSFW. Also there's probably malware or something.
Further forensic analysis (including adding and removing stuff at the beginning and end, and grepping the line out, and sending the line all by itself) determined conclusively that it was that specific string that was giving Exchange the old digital shiv in the ribs. There's something hard-coded into it that makes it silently discard your message if it should happen to have "consumptionjunction.com" anywhere in the message body. It makes Exchange a splode.
It's been one of those Mondays.
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Brian Tiemann
