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No MX record in DNS

Posted on 2011-03-08
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I do not see an MX record listed in my forward look up zone.  Is it required?  Will adding one hurt anythong? For the most part, our email system (Exchange 2003) works fine.  We even have a printer that can send a scan to a computer by way of SMTP and that works fine.  However, we have an inbox account in Outlook 2003 that is setup as IMAP4/SMTP.  We can receive emails to this account but cannot send emails from it.  Would this even be related?  (Especially since the printer can send email by way of SMTP).  
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Question by:tmaususer
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by:CHutchins
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If Exchange is working for external email you would have to have an MX record otherwise you would get loads of bounce backs.  

If you cannot send on the SMTP account it would be because it is configured wrong on the client.  
Might be an SSL setting incorrect SMTP server information or even login credentials for SMTP.
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PaciB earned 250 total points
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Hi,

An MX record is necessary on external DNS servers to permit external senders to send e-mails to your company. So, somewhere on a DNS server on Internet, your SMTP domain name must be declared and must contain an MX record that points to the SMTP server that is the "entrance" of your company.

Now, about your internal network, usually you don't need to declare an MX record in your internal DNS because your e-mail clients (Outlook or any other) are probably configured to deliver all mails to your Exchange server. If you use Outlook as a MAPI client you type the Exchange server name in the Outlook profile during configuration, if you use Outlook as a POP/IMAP client (or any other POP/IMAP client) you probable type the Exchange server FQDN as the SMTP and POP server.
So, your clients do not need to locate the server because you explicitly mentioned it in the client configuration.

The fact that your IMAP4/SMTP client can not send e-mail is probably due to a misconfiguration of the Exchange SMTP virtual server object or of the client. First of all, the problem is about SMTP as it is this protocol that is used to send mails, IMAP4 is used to read mails.

The first check you should do to verify is the server is well configured to receive SMTP trafic from your client is the following:
From your client computer (the one that hosts the IMAP4/SMTP client) open a CMD console. In the CMD console type the command "TELNET xxx.xxx.xxx.xxx. 25" where xxx.xxx.xxx.xxx is the IP addresse of your Exchange server.
If the SMTP session can be established, the CMD screen should turn to black with a blinking cursor at top left during 1 second and then you'll probably see a SMTP banner. That proves that the server is well configured to accept SMTP incoming trafic from yoru client.

After that, you'll have to check the client configuration. Verify that SMTP server IP address is well configured on the client. If your use a nem instead of an IP address make sure that you type the FQDN of the server.
Also, you must ensure that the SMTP e-mail address mentioned in the client configuration is good and matches your SMTP suffix. As an example, if your Exchange SMTP domain is @mydomain.com, your SMTP client must be configured to used a sender e-mail address like "username@mydomain.com". If not, when your SMTP client starts to dialog with the Exchange server to send an e-mail, the Exchange server might refuse the message because the sender e-mail address does not match the internal SMTP domain.


Have a nice day



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by:tmaususer
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Hello, PaciB.  Thank you for the helpful information.
I now understand that the MX record is on our domain host's servers.

I am not able to telnet to port 25 on the exchange server from the client; however, I am able to telnet from the Cisco switch.  I did try disabling our antivirus on the client and still could not telent the port.  Does this tell me that the switch is configured okay, but the client is not?

Also, I am not quite sure I understand when you said "After that, you'll have to check the client configuration. Verify that SMTP server IP address is well configured on the client."  Are you refering to how Outlook is configured on the client?
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by:tmaususer
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Thanks you CHutchins for your clarification.
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