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  1. #1
    SitePoint Zealot
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    replying to an email, but that user doesn't exist!

    Not a development issue per se, but ...

    i'm just wondering about some of these returned emails that i get sometimes. i reply right to the address that the message came from but then it bounces saying that the user is 'unknown'. what the????

    Here is the error message I get ... of course the email address is fake here
    A message that you sent could not be delivered to one or more of its
    recipients. This is a permanent error. The following address(es) failed:

    jfsabastian@some_domain.com
    SMTP error from remote mailer after RCPT TO: <jfsabastian@some_domain.com>:
    host mail.some_domain.com [00.000.00.00]: 550 unknown user <jfsabastian@some_domain.com> ...
    What could be the problem??

    Thanks!

  2. #2
    SitePoint Addict
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    Normally these are responses to bulk spam email, which is generally quite easy to do if you have your own mail server or access to one which is not secured. It's easy to write a program that creates a thousand email addresses, all with a bogus (or each with their own bogus) from-address. The mail server then sends the emails, and any that are sent to people who have junk protection, or non-existent email addresses (because the list was old, or was random made-up addresses) will 'bounce' back to the from-address. But, the from-address will be made up, so the spammer doesn't get them, whoever owned the from-address will get them. But if this is happening, then the problem is that the to-address the spammer used did not exist, therefore that becomes the 'from' address for your bounce message, so it still doesn't exist when you try to email it.

    The SPF record is supposed to help address problems like this, but a number of commercial ISPs don't implement it because it's not a 'perfect' solution. I tried to explain to my ISP that I'd rather have an imperfect solution than keep getting more than 1000 of these 'bounce' messages every night, but they weren't interested.

  3. #3
    SitePoint Zealot
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    Thanks droopsnoot, the thing is its a legit human email asking about their order on our site, he is a customer! (sorry didn't say so earlier) Checking more closely, he used another email on one of his replies, but the email he wrote to me on cannot be replied to because it doesn't exist! (or so it seems ... hmm) How can this be?

    Can Spam blocking software throw that kind of 'unknown user' message?
    Last edited by abb; Oct 6, 2006 at 01:17. Reason: typos

  4. #4
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    I don't know much about spam blocking software. But it wouldn't be the first time that I've received an email from a user but they have an incorrectly spelt the 'reply-to' address configured in their email client. Not all email programs honour the 'reply-to' address and use the 'from' address instead, so he might get replies from others but not from you. Or maybe the 'from' address is badly spelt.

    I have a few subscribers with 'bad' email addresses and every time we send a mailshot, we get them bounced back. For our site, we have a subscribers login area so I'm doing a 'message to subscriber' feature that will prompt them to fix it when the login to the site, but of course I can't email the people concerned to alert them, so then we get emails complaining that they don't get notification of updates, etc.

    Some mail servers will check the sending domain to a varying degree to make sure that it's legit, and they don't usually let on how the checks are being made. My email sometimes gets reject if I send an email to the BBC, and it comes back with "domain does not exist". I think "unknown user" is very specific, though - the mail server is saying that it doesn't have a mailbox with that name.

  5. #5
    SitePoint Wizard LiquidReflex's Avatar
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    It can happen since a lot of the time the user will configure their own mail client. If they type in their own email address incorrectly, it will send using that as the "from". Since most mail clients don't check what the user puts in as their email address (only their account ID, password and SMTP info) to send a message, it can happen often.
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  6. #6
    SitePoint Zealot
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    But it wouldn't be the first time that I've received an email from a user but they have an incorrectly spelt the 'reply-to' address configured in their email client.
    LOL, I bet that is the case!! its kind of funny that this could happen and very inconvenient!

    For our site, we have a subscribers login area so I'm doing a 'message to subscriber' feature that will prompt them to fix it when the login to the site
    Great idea, probably thats what we have to do too, get members to eyeball and confirm their email address.

    Much appreciated droopsnoot, and thank you LiquidReflex!
    Last edited by abb; Oct 6, 2006 at 09:40. Reason: nothing much


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