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Can't get Exchange Server to Send Email using DNS

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by carl

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I have a new installation of SBS 2003 with Exchange Server. I can receive email with the pop3 connector, but am unable to send emails using DNS to route email. I can send email using the "forward all e-mail to e-mail server at your ISP", but this, I believe, can result in some of the email I send being treated as Spam as it will have been been forwarded. Currently I am I am unable to send to hotmail accounts for example.
If I am only using DNS routing to send email is it necessary for me to have an MX record and/or a fixed IP address?

2 replies

by techsoeasy

First, your assumption that you need a fixed IP address to send SMTP email from Exchange is not valid. You can most definitely use a dynamic IP to send, you just need to use a service like DynDNS.org's MailHop.

Now this actually brings up another misconception of yours... that relaying your outbound mail is what's causing Hotmail to reject it. Hotmail uses a version of SenderID to decide whether or not to reject mail. (see: http://postmaster.msn.com/Services.aspx#SenderSolutions)

Your first step to overcomming that problem is to create an SPF record in your domain's DNS zone file (see: www.openspf.org). If you use www.DynDNS.org's Custom DNS service (only about $25/year) you can easily add this record per their instructions.

Now, to the actual problem of why you can't send via DNS? Most likely your Internet Access Provider is blocking port 25. This is quite common, and they generally allow port 25 traffic only to their own SMTP servers so they can monitor whether or not a subscriber is sending SPAM. Again, www.DynDNS.org allows for outbound SMTP traffic on an alternate port to work around this.

Jeffrey B. Kane [MVP] Small Business Server
www.TechSoEasy.com

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