This morning in my inbox, I had two bounce messages--nothing unusual there, it seems to happen quite often when I try to email users of macosxhints.com (lots of people have changed their email addresses but not changed their account info, it seems).
These two messages, however, really caught my eye; here's a snippet from one of them. Note that I've modified the email address, but that's all:
'5.1.1 No such user 10si9367260nzo' (delivery attempts: 0)
From: [email protected]
Date: August 24, 2007 8:20:25 AM PDT
To: robg
The following message to <[email protected]> was undeliverable.
The reason for the problem:
5.1.0 - Unknown address error 550-'5.1.1 No such user'
From: Rob Griffiths <robg>
Date: February 24, 2002 7:04:21 PM PST
To: Some User <[email protected]>
Subject: Re: Mac OS X Hints Redesign
. . .
Yes, that's right: two messages I sent over five years ago finally bounced early this morning! Not knowing the first thing about how email actually routes between machines, can someone explain how this might be possible? It seems too bizarre to believe, but the messages are mine, and I did try to send them to the specified person back in 2002. Very weird! Explanations welcomed, please...
Please, show us the FULL header of your original mail and the reply from the mailer so we can see where it was stuck...
When you send email, you connect to an SMTP server, typically one provided by your business or by your ISP. (SMTP stands for Simple Mail Transfer Protocol.) It's analogous to dropping a letter in the slot at the post office.
Your mail program passes the SMTP server an "envelope" section with all the destination addresses, and a "content" section, which includes the message and all its visible headers. This is how things like BCC work -- your email program puts the destination addresses into the envelope section, but leaves the BCC line out of the content section.
The SMTP server writes out a copy of your message for each destination hostname. If you send a message to five people at apple.com and two at aol.com, we'll put the five Apple addressees in the envelope section of a copy for Apple, and we'll put the two AOL addressees into the envelope section for AOL's copy.
The SMTP server's job is to deliver local mail to individual users' mailboxes, and to "relay" non-local messages to an appropriate SMTP server which takes responsibility for delivering the message.
A delivery job does a DNS query on each hostname, preferring MX (Mail eXchange) records to standard DNS address records. MX records allow mail to be handled by different machines than those handling other domain traffic.
The delivery job will attempt to make a connection to each mail host. Multiple addressees at a particular host are the responsibility of the server at that host.
There may be more than one relay. For example, Apple might have internal SMTP servers for each department, and some departments might have their own internal servers. Each server is responsible for relaying the message one step along the route, and problems might occur at any step.
Some errors are permanent. If my employer fires me and deletes my email account, anyone sending email to my old address should get a bounce message saying, in effect, "Never heard o' the bum!" This kind of bounce often happens immediately -- the SMTP server might refuse to accept the message at all.
Other errors are temporary. If we can't connect to apple.com right now, it might be a temporary network problem, or system maintenance time, or some other short-term problem. The mail protocols try to be robust, so servers store the message and try again later. Typically, a scheduled job runs every few hours to retry stalled messages. Server parameters say how long to keep trying. When time runs out, you'll get a bounce message saying something like, "We were unable to deliver your message after trying for ten days." (This is why some bounce messages arrive days after you sent the message.)
This particular bounce is not a time-out after five and a half years of trying to deliver your message, because the reason is "No such user." My guess is that your message wound up on an SMTP server where, due to configuration error or some other problem, there was NO scheduled job running to retry stalled messages, and the people responsible for the SMTP server didn't understand the system well enough to spot the problem. Then, on August 24, something changed -- the retry job ran, and tried to relay your message. But by this time, the user account was no longer valid, so the message was "immediately" bounced to you.
If you're still awake, hope this helps.
I got one of these too, from a message I sent to the same person in 2003. They were delivered correctly in the first place (you can see this in the headers of the forwarded message), but the user is attempting to use SMTP to migrate his mail to Gmail. However, the Gmail address was undeliverable, probably because the account was closed for abuse.
Unfortunately, the user didn't set up his migration correctly. Instead of connecting directly to Google's SMTP server, where it would be possible to see the SMTP errors locally, he sent the mails through Postfix on his Mac to his ISP's mail server first, which was the server that bounced things to us. To the user, it looked like things were going great, but all it was doing was spraying bounces of all his mail to the rest of us.
Why was the Gmail account closed? My guess is because it received too much mail too fast. I did a similar SMTP migration (successfully) in January with about three years' worth of mail, but I used Python to connect directly to Google's SMTP servers from my Mac and waited 2 seconds between each mail delivery. I also used ClamAV on the messages first, since I had a lot of virus-laden attachments and Google rejected them before delivery. This meant the transfer took weeks, but it also worked successfully and my account still exists! The major problem was false positives in Gmail's spam filtering; the original mail was not filtered and Gmail doesn't seem equipped to handle multi-year-old mail, so I had to manually scan all the spam.
My script was derived from the script here.
I had to change some things to protect some email addresses, so here's the key:
So with that in mind, here's the full header:
Hopefully that makes sense to someone :).
-rob.
Here's were it stuck.... Likely this server died or otherwise stopped working for sometime (decommissioned) , and was later turned back on.
Received: (qmail 63855 invoked from network); 25 Feb 2002 03:04:30 -0000
Received: from rwcrmhc51.attbi.com (204.127.198.38)
by pop3-2.domain1.com with SMTP; 25 Feb 2002 03:04:30 -0000
Physicists will tell you time travel is not possible. Why? Time itself simply does not independently exist. It is dependent on the changing topology it temporaryily inhabits. In relativistic terms, mass deforms the space it occupies because of its aggregate rest and kinetic energies. Energy does change the the structure of the space around it. The faster the rate of change the slower the movement of time to where at infinitie energy E=C2(squared), or Energy equals the speed of light squared and the mass drops out into 1. This is virtually impossible by the lorentz contraction and if you do the math you will see the problem. Its this difference that is the time that it takes the event displacement to happen. You cannot reverse the process as its linearly cummulative. That is why the speed of light is constant no matter what frame of reference you look at it from. Time then is nothing more than a lens of action at a distance. As the kinetic energies increase, time slows down and lenght contracts. Key here is one question and that is what is the topology involved? Our so called 3 dimensional universe isn't really that as its constantly deforming as we walk through our living room. In our biologic world we can't measure it, though our most sensitive instruments can given an extreme experiment. Rather than think about the clock ticking as we walk across the room, try thinking of the spatial dimensions collapsing in on you as you accelerate or decelerate your movements. That is the motor of corporal time, atomic time, particulate time. Since the existance of all particles is only measureable as wave interferences at a point in time, you might ask then just what on earth is really happening then? Welcome to quantum physics which is the real story. In quantum mechanics time itself is just an operator or set of conditions that sets up the equations. Time quickly becomes an artifice. Its not real in the sense we mammals think of it.
Comments are closed.