Last Thursday, I obediently installed a number of Windows Updates. It all went fine. Once I had rebooted, I was no longer able to send via my personal email account. Odd, but I had seen it before. Rebooting (and maybe scanpst’ing) had fixed it before, so I did those two things. No luck.

I finally fixed it, but mysteries remain.

I double-checked the name and password on the account. They were fine. My ISP (RCN) requires that I use their SMTP server for sending outgoing mail, even though I don’t use their POP server for receiving mail. My wife and son both use the same outgoing SMTP server with the same credentials, and they were able to send email, so I was confused.

The onset of the problem coincided with my installation of Windows Updates, and only affected the one computer in three that had the Updates, so I naturally believed they were at fault. Naively believing in a Newtonian universe, I read the knowledgebase articles about the fixes to see which sounded like it might be somewhere near an email stack. I picked the most likely one and uninstalled it. No change.

Next, I used telnet to connect directly to the SMTP server (this tutorial on SMTP authentication proved useful as a guide). Sure enough, the server rejected my username and password. I tried telnet’ing from my wife’s Mac, just in case somehow the OS was interfering. Nope, the credentials were rejected there too. But my wife could send mail. Checking her email account settings, I see that she’s actually going in anonymously! I set the username and password, and she can still send email.

Next, I wrung my hands for a long time, and bemoaned my fate, and generally got depressed about the impossibility of understanding and troubleshooting the complexity of modern computer systems.

Next, I installed Ethereal to capture the network traffic to see what is happening. No surprise there: it shows Outlook doing just what I had done with telnet, and being denied access.

Having figured out Ethereal enough to watch network traffic on a Windows machine, I figured I might as well install it on my son’s computer to see how it is managing to send email. Here’s the strangest part: He was sending the same credentials as me, and also being returned an “authentication failed” message. But his Outlook Express simply ignored the error and sent the email anyway, and the SMTP server gladly accepted it and delivered it!

To reiterate: the client-server interactions that worked went like this:

1. Client: Let me in, it’s ned.
2. Server: I don’t believe you: you can’t come in.
3. Client: Screw you, I’m coming in anyway!
4. Server: That’s OK, I was just kidding!

Is this the state of SMTP security? No wonder we have a spam problem!

So now at least I understand why some email was getting through, but what’s wrong with the credentials anyway? Next I went to my account page at RCN to see if the username and password are correct. After all, the “successful” credentials were being flagged as wrong anyway, so maybe I didn’t know my password?

At the RCN account page, sure enough, it accepted my username and password, so it turns out I did know them after all. I was about to change the password just to see if that would flush out some frogs, when I notice one of the options on the page: “Reactivate your email account”.

Aha! Turns out that since I never use the POP half of my email account, they decided to deactivate it. Reactivating it made everything work, at last!

Remaining mysteries:

1. Why didn’t RCN try sending me an email to let me know the account was being deactivated. (I checked the POP account: there’s no mail there, although maybe they dumped it when they deactivated it.)
2. Why didn’t RCN notice that the SMTP side of the account was quite active, thank you very much, and leave everything as it was?
3. Why “deactivate” the account so that credentials fail, but then accept email anyway?
4. Was the account deactivated last Thursday, or was one of the Windows Updates a fix so that Outlook would notice the credentials were deactivated?
5. What do ordinary people do to keep their computers running smoothly?