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Recipient address rejected: User unknown from external emails only RRS feed

  • Question

  • We manage a company that is using SBS2003 with Exchange 2003 and we just created 2 new accounts through the SBS wizard which created email accounts for them. When anyone from outside the company tries to send them and email we get an error of "Recipient address rejected: User unknown."  I have also tried by telneting directly to their server from the outside and get the same error. Telneting internally it works as does all internal emails to and from the user. The user can also send out. The only failure is incoming to this new user and new test user. They don't go through any spam filtering service and so far I have been unable to locate any AV or locally installed spam filter.. Any suggestions?
    Wednesday, August 22, 2012 9:05 PM

Answers

  • On Wed, 22 Aug 2012 21:05:49 +0000, C-M wrote:
    >We manage a company that is using SBS2003 with Exchange 2003 and we just created 2 new accounts through the SBS wizard which created email accounts for them. When anyone from outside the company tries to send them and email we get an error of "Recipient address rejected: User unknown." I have also tried by telneting directly to their server from the outside and get the same error. Telneting internally it works as does all internal emails to and from the user. The user can also send out. The only failure is incoming to this new user and new test user. They don't go through any spam filtering service and so far I have been unable to locate any AV or locally installed spam filter.. Any suggestions?
    Do you see the rejection in the SMTP protocol log? If not, it's not
    Exchange thats the problem.
    What's different between the "internal" and "external" address? Is
    there some sort of SMTP proxy that needs to be updated with new
    addresses?
    ---
    Rich Matheisen
    MCSE+I, Exchange MVP

    --- Rich Matheisen MCSE+I, Exchange MVP

    I figured there had to be some type of spam filter or user filtering
    but for the life of me I can't locate anything. When I telnet in this is
    what I am seeing

    220 mail.theirdomain.com ESMTP Postfix
    EHLO test
    250-mail.theirdomain.com
    250-PIPELINING
    250-SIZE 75000000
    250-VRFY
    250-ETRN
    250 8BITMIME
    Mail From:user@user.com
    250 Ok
    RCPT TO:testuser@theirdomain.com
    550 <testuser@theirdomain.com>: Recipient address rejected: User unknown


    Ok I think I figured this out. They are using a linux firewall and using it as a smarthost relay... now to find out if anyone knows the password.
    • Proposed as answer by Jamestechman Thursday, August 23, 2012 5:17 PM
    • Marked as answer by Fiona_Liao Thursday, August 30, 2012 1:43 AM
    Thursday, August 23, 2012 4:09 PM
  • On Thu, 23 Aug 2012 15:12:36 +0000, C-M wrote:
     
    >On Wed, 22 Aug 2012 21:05:49 +0000, C-M wrote: >We manage a company that is using SBS2003 with Exchange 2003 and we just created 2 new accounts through the SBS wizard which created email accounts for them. When anyone from outside the company tries to send them and email we get an error of "Recipient address rejected: User unknown." I have also tried by telneting directly to their server from the outside and get the same error. Telneting internally it works as does all internal emails to and from the user. The user can also send out. The only failure is incoming to this new user and new test user. They don't go through any spam filtering service and so far I have been unable to locate any AV or locally installed spam filter.. Any suggestions? Do you see the rejection in the SMTP protocol log? If not, it's not Exchange thats the problem. What's different between the "internal" and "external" address? Is there some sort of SMTP proxy that needs to be updated with new addresses? ---
    >Rich Matheisen MCSE+I, Exchange MVP
    >--- Rich Matheisen MCSE+I, Exchange MVP
    >
    >I figured there had to be some type of spam filter or user filtering but for the life of me I can't locate anything. When I telnet in this is what I am seeing
    >
    >220 mail.theirdomain.com ESMTP Postfix EHLO test 250-mail.theirdomain.com 250-PIPELINING 250-SIZE 75000000 250-VRFY 250-ETRN 250 8BITMIME Mail From:user@user.com 250 Ok RCPT TO:testuser@theirdomain.com 550 <testuser@theirdomain.com>: Recipient address rejected: User unknown
     
    Postfix isn't Exchange. :-)
     
    If they don't have Postfix set up to use LDAP then they're probably
    doing some sort manual update to the file in the local_recipient_maps
    parameter in the main.cf file.
     
    ---
    Rich Matheisen
    MCSE+I, Exchange MVP
     

    --- Rich Matheisen MCSE+I, Exchange MVP
    • Proposed as answer by Fiona_Liao Friday, August 24, 2012 6:38 AM
    • Marked as answer by Fiona_Liao Thursday, August 30, 2012 1:43 AM
    Friday, August 24, 2012 1:36 AM

All replies

  • On Wed, 22 Aug 2012 21:05:49 +0000, C-M wrote:
     
    >We manage a company that is using SBS2003 with Exchange 2003 and we just created 2 new accounts through the SBS wizard which created email accounts for them. When anyone from outside the company tries to send them and email we get an error of "Recipient address rejected: User unknown." I have also tried by telneting directly to their server from the outside and get the same error. Telneting internally it works as does all internal emails to and from the user. The user can also send out. The only failure is incoming to this new user and new test user. They don't go through any spam filtering service and so far I have been unable to locate any AV or locally installed spam filter.. Any suggestions?
     
    Do you see the rejection in the SMTP protocol log? If not, it's not
    Exchange thats the problem.
     
    What's different between the "internal" and "external" address? Is
    there some sort of SMTP proxy that needs to be updated with new
    addresses?
     
    ---
    Rich Matheisen
    MCSE+I, Exchange MVP
     

    --- Rich Matheisen MCSE+I, Exchange MVP
    Wednesday, August 22, 2012 10:19 PM
  • Hi,

    If you create a new user with Exchange mailbox enabled in ADUC, can  you reproduce this issue?

    What is the NDR message?

    thanks.


    Fiona Liao

    TechNet Community Support

    Thursday, August 23, 2012 9:14 AM
  • On Wed, 22 Aug 2012 21:05:49 +0000, C-M wrote:
    >We manage a company that is using SBS2003 with Exchange 2003 and we just created 2 new accounts through the SBS wizard which created email accounts for them. When anyone from outside the company tries to send them and email we get an error of "Recipient address rejected: User unknown." I have also tried by telneting directly to their server from the outside and get the same error. Telneting internally it works as does all internal emails to and from the user. The user can also send out. The only failure is incoming to this new user and new test user. They don't go through any spam filtering service and so far I have been unable to locate any AV or locally installed spam filter.. Any suggestions?
    Do you see the rejection in the SMTP protocol log? If not, it's not
    Exchange thats the problem.
    What's different between the "internal" and "external" address? Is
    there some sort of SMTP proxy that needs to be updated with new
    addresses?
    ---
    Rich Matheisen
    MCSE+I, Exchange MVP

    --- Rich Matheisen MCSE+I, Exchange MVP

    I figured there had to be some type of spam filter or user filtering
    but for the life of me I can't locate anything. When I telnet in this is
    what I am seeing

    220 mail.theirdomain.com ESMTP Postfix
    EHLO test
    250-mail.theirdomain.com
    250-PIPELINING
    250-SIZE 75000000
    250-VRFY
    250-ETRN
    250 8BITMIME
    Mail From:user@user.com
    250 Ok
    RCPT TO:testuser@theirdomain.com
    550 <testuser@theirdomain.com>: Recipient address rejected: User unknown


    Thursday, August 23, 2012 3:12 PM
  • On Wed, 22 Aug 2012 21:05:49 +0000, C-M wrote:
    >We manage a company that is using SBS2003 with Exchange 2003 and we just created 2 new accounts through the SBS wizard which created email accounts for them. When anyone from outside the company tries to send them and email we get an error of "Recipient address rejected: User unknown." I have also tried by telneting directly to their server from the outside and get the same error. Telneting internally it works as does all internal emails to and from the user. The user can also send out. The only failure is incoming to this new user and new test user. They don't go through any spam filtering service and so far I have been unable to locate any AV or locally installed spam filter.. Any suggestions?
    Do you see the rejection in the SMTP protocol log? If not, it's not
    Exchange thats the problem.
    What's different between the "internal" and "external" address? Is
    there some sort of SMTP proxy that needs to be updated with new
    addresses?
    ---
    Rich Matheisen
    MCSE+I, Exchange MVP

    --- Rich Matheisen MCSE+I, Exchange MVP

    I figured there had to be some type of spam filter or user filtering
    but for the life of me I can't locate anything. When I telnet in this is
    what I am seeing

    220 mail.theirdomain.com ESMTP Postfix
    EHLO test
    250-mail.theirdomain.com
    250-PIPELINING
    250-SIZE 75000000
    250-VRFY
    250-ETRN
    250 8BITMIME
    Mail From:user@user.com
    250 Ok
    RCPT TO:testuser@theirdomain.com
    550 <testuser@theirdomain.com>: Recipient address rejected: User unknown


    Ok I think I figured this out. They are using a linux firewall and using it as a smarthost relay... now to find out if anyone knows the password.
    • Proposed as answer by Jamestechman Thursday, August 23, 2012 5:17 PM
    • Marked as answer by Fiona_Liao Thursday, August 30, 2012 1:43 AM
    Thursday, August 23, 2012 4:09 PM
  • On Thu, 23 Aug 2012 15:12:36 +0000, C-M wrote:
     
    >On Wed, 22 Aug 2012 21:05:49 +0000, C-M wrote: >We manage a company that is using SBS2003 with Exchange 2003 and we just created 2 new accounts through the SBS wizard which created email accounts for them. When anyone from outside the company tries to send them and email we get an error of "Recipient address rejected: User unknown." I have also tried by telneting directly to their server from the outside and get the same error. Telneting internally it works as does all internal emails to and from the user. The user can also send out. The only failure is incoming to this new user and new test user. They don't go through any spam filtering service and so far I have been unable to locate any AV or locally installed spam filter.. Any suggestions? Do you see the rejection in the SMTP protocol log? If not, it's not Exchange thats the problem. What's different between the "internal" and "external" address? Is there some sort of SMTP proxy that needs to be updated with new addresses? ---
    >Rich Matheisen MCSE+I, Exchange MVP
    >--- Rich Matheisen MCSE+I, Exchange MVP
    >
    >I figured there had to be some type of spam filter or user filtering but for the life of me I can't locate anything. When I telnet in this is what I am seeing
    >
    >220 mail.theirdomain.com ESMTP Postfix EHLO test 250-mail.theirdomain.com 250-PIPELINING 250-SIZE 75000000 250-VRFY 250-ETRN 250 8BITMIME Mail From:user@user.com 250 Ok RCPT TO:testuser@theirdomain.com 550 <testuser@theirdomain.com>: Recipient address rejected: User unknown
     
    Postfix isn't Exchange. :-)
     
    If they don't have Postfix set up to use LDAP then they're probably
    doing some sort manual update to the file in the local_recipient_maps
    parameter in the main.cf file.
     
    ---
    Rich Matheisen
    MCSE+I, Exchange MVP
     

    --- Rich Matheisen MCSE+I, Exchange MVP
    • Proposed as answer by Fiona_Liao Friday, August 24, 2012 6:38 AM
    • Marked as answer by Fiona_Liao Thursday, August 30, 2012 1:43 AM
    Friday, August 24, 2012 1:36 AM
  • If no more questions on this thread, we may mark it as answered. Thanks.

    Fiona Liao

    TechNet Community Support

    Monday, August 27, 2012 10:10 AM