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Linux, Unix, and *nix like Operating Systems Forum

DNS Setup and Email Deliverability
A dedicated IP on a server might hurt email deliverability?

 2:08 pm on Feb 28, 2008 (gmt 0)

I have a dedicated linux server that has 16 IP addresses... and one of those IP address is the main (or shared) IP of the server. So I can host a ton of websites on that one shared IP, and can optionally move individual accounts to one of the 15 other dedicated IP's if I so desire.

I put an account on it's own dedicated IP and it works fine. But I've noticed all my email being sent out is being filtered into people's spam folders... be it hotmail, gmail, yahoo, outlook, etc. My DNS is setup great as far as I can tell (DNSreport confirms) and I have SPF/domainkeys installed for this one account... so I shouldn't have problems authenticating my emails.

The only thing I can think of that would be causing problems for my mail being filtered as spam, is that since this account is on one of my dedicated IP's... that these mail providers (yahoo, etc) are looking at the incoming connection claiming to be the host, which is the main (or shared) IP of the server, and then looking at the MX record for the domain that the email address is, which points to that dedicated IP... and since they don't match... the email provider rejects the email cause the two IP's aren't matching.

Is this a valid assumption? And if so, is there anything I can do about it besides moving that one account back to the shared IP? For the life of me I can't figure this out.

Thanks for your help guys.



 4:11 pm on Feb 28, 2008 (gmt 0)

You should send an email to an account you have access to and look in the email header which IP address is really used to send the message. This IP address should be in your SPF configuration.

Then check if the IP address has a reverse DNS entry. Without a reverse DNS entry, the email will probably be marked as spam.

Third, you should check on internet block list checkers if that IP address has been used by spammers in the past. Maybe an IP address with a bad history was assigned to you.


 12:31 am on Feb 29, 2008 (gmt 0)

MX has NOTHING to do with sending mail - only receiving. So, nobody is going to check the MX record to see if the sender matches.

Make sure that you have the IP address that you are sending from listed in the SPF record. NOT the address of your mail exchanger.

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