WhiteSites Blog

MX records being used to block spam

Posted on Apr 20, 2009 by Paul White

If you run any kind of bulk mail server, you have probably already dealt with yahoo's temporary blacklisting of your IP.  They force you to fill out a bunch of forms asking you about your setup.  For one of my clients we are running a unique setup.

Windows 512 MB VPS - for website, newsletter, and automated emails

Linux Shared Hosting account - for Smarter Stats, Smarter Mail ( corporate emails ), MySQL

A 512 MB VPS just isn't big enough for everything, and its more cost effective to off shore services to a shared hosting account. 

What makes this unique is we are running two mail servers.
Smarter Mail on the Shared Linux box ( MX records points to here )
Virtual SMTP on the VPS ( no MX record )

We do have Reverse DNS setup correctly, along with SPF for both servers.

The problem is after we do a blast to our 6000 reciepients, we are only able to track about 450 of them.  The first time we did a blast we had almost 700 confirmed reads.  The number has been dropping slowly over time. 
After a while I started to assume that most of the emails were getting blocked or ending up in people's spam folder where it would be destined for deletion. I thought 10% read was pretty good.

Recently after settting up another client of mine, I was having trouble using the HMS list server.  Emails were not going through.  This lead me to believe that the IP of the list server has become blacklisted or something similar that would cause the big mail servers to not let through the emails.  This client only had 60 emails in his list. so I setup his newsletter to relay through his Smarter Mail Server ( MX record points to ).  Normally the hosting company recommends we not do this but with such a small number of emails, I figured it wouldn't affect the server.  Amazingly I was able to track 40 of the 60 emails were opened within 24 hours of sending.

So sending bulk emails from the server that my MX points to seems to get me a much higher success rate.  This leads me to believe that many Mail Servers are now considering any email that comes from your non MX mail server to be bulk or spam. 

To test this I will be doing a blast with my larger client this week.  I will be sending them through our MX pointed mail server, to see if we have a higher success rate.

UPDATE 4/27/2009

I sent out our last newsletter via our MX based mail server and there was no improvement in the open rates.  So I guess my theory has been busted.

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