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Exchange 2007 uses direct DNS for all outgoing mail. Mail that is sent from our public IP (1.2.3.4 - this is the IP of my mailserver) is delivered to the spam folders for providers such as Comcast and yahoo.

Currently, our SPF looks like this: v=spf1 ip4:1.2.3.4 mx a:mail.domain.com ?all

MX: mail.domain.com.(10)

The reverse DNS entry on our ISP is mail.domain.com for our IP

The banner HELO response from our server is <220 mail.domain.com>

Our IP address is NOT blacklisted anywhere, and the Cisco Senderbase gives us a score of Good

What is the reason our mail doesn't look legit?

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Presumably you can get sample emails from the messages delivered to these spam folders and look at the headers? Lots of valuable information in headers. –  RobM Dec 21 '10 at 22:52
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3 Answers

up vote 0 down vote accepted

Everything is functional now, had to make a minor adjustment in our SPF and also just needed time for our DNS to propagate.

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as you told me that I got something wrong, just help me to help you :)

Mail and DNS hosted with Network Solutions. MX records only point to NetSol. Exchange POP connector used to download mail to our Exchange mailboxes.

Both is ok.

Exchange 2007 uses direct DNS for all outgoing mail. Mail that is sent from our public IP (1.2.3.4) >is delivered to the spam folders for providers such as Comcast and yahoo. When they reply to that >mail, it is never received by us.

This looks a lot like a wrong setup of the MX-records or an error somewhere in the mail system. Normally the e-mail should hit at your providers mailbox and then you should get it via pop3 connector. As this doesn't happen. Check the MX-records and check any spam folders available at your providers mail system. (POP3-connector isn't downloading subfolders iirc).

If we login to the NetSol webmail portal (mail.ourdomain.com), and send mail to Comcast or yahoo, >the message is received normally, and we receive replies. My thought is that once the message is >marked as spam, their reply never gets to us, as the NetSol spam filters are extremely aggressive, >and drop the message. We have no control/access to these filters or logs of what is filtered. But >why are we being marked as spam?

I'm pretty sure this problem comes from wrong mx- or spf-records. When you send an e-mail via the netsol web ui, it's delivered ok, because it's delivered via the netsol smtp which is setup correctly in dns...

Currently, our SPF looks like this: v=spf1 ip4:1.2.3.4 mx a:inbound.ourdomain.com.netsolmail.net ?all

MX: inbound.ourdomain.com.netsolmail.net.(10) with CNAMES of mail.ourdomain.com and smtp.ourdomain.com

The reverse DNS entry on our ISP is ourdomain.com for our IP

"Our IP"? From the webserver of from the mail system?

The banner HELO response from our server is <220 ourdomain.com> Our IP address is NOT blacklisted anywhere, and the Cisco Senderbase gives us a score of Good

As I wrote before it has something todo with your dns setup. But I'm only able to check it if you give me the domain we're talking about.

KR,

Gromit

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The IP is the one in front of my mail server. Receiving mail at a host, and sending directly from your own server is quite common, as well. –  DanBig Dec 2 '10 at 0:05
    
Also, in my post, i stated that I am unable to view spam folders from NetSol. –  DanBig Dec 2 '10 at 13:05
    
Hi, you wrote that the MX records only point to NetSol. If your mailserver delivers mail directly the mx records don't match and it's tagged as spam. In 95% of the cases it's a DNS problem. –  gromit Dec 2 '10 at 16:57
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if i get this straight:

your domain is registered to the mailservers of your provider and your mailserver is delivering the mails directly. So when the mail is delivered the reverse lookup of the ip can faile (1st spam hit), then the receiving mailserver sees an spf that is not pointing to your system (2nd spam hit) and your system is only listed as IP address in SPF record (maybe spam hit #3) and the incoming direction is routed via a different system, which is not 100% clear by the information you gave (spam hit #4).

This also explaines why it's working when you try to deliver mail via the web interface.

Just tell your exchange box to send all outgoing mail via the providers smtp server and everything should be fine again.

KR,

gromit

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You read wrong. My SPF is allowing my IP to send. My reverse record points my domain to my IP. –  DanBig Dec 1 '10 at 22:59
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