First, let me preface my questions with the following comments. Due to Hurricane Ike hitting Houston and causing significant power problems, I contracted with Dell MessageOne to provide backup email service for my users. The power to our offices went down at approximately midnight on Friday (12th) and, when I realized this around 2:30am Saturday morning, I activated the backup service. Power didn't return until around 4:00pm on Sunday (14th) and I did not switch back over from the backup service until 9:30pm on Monday night. During this time my users we fully able to access their email and conduct business with only minor frustration. Since Monday night we have been fully operational just as we were before the storm.
However, on Wednesday I had an email to my sales rep at Dell.com returned as undeliverable after 2 days (sent on Monday from backup service), which is the timout I have configured on my email server. While investigating, I tried connecting via telnet to Dell's SMTP server and received the following error;
554 Connections from this sending hostname 220.127.116.11.ptr.us.xo.net, IP address of: 18.104.22.168 are being rejected due to low SenderBase Reputation score (below -2). Your SenderBase organization: 4162354. See http://www.senderbase.org/ for more information.
So, I immediately kicked off a company-wide virus scan (Symantec Enterprise Edition) and began other research to figure out what is going on.
I started by checking the blacklists (http://www.mxtoolbox.com/blacklists.aspx?AG=GBL&gclid=CL2L8-Lv6JUCFRIcawodqEsueQ) and our IP address isn't listed on any of them.
I then went to SenderBase.org and looked up our IP address and found the reputation to be poor. The volume statistics show a magnitude of 2.7 for the last month but 0.0 for the last day. Nothing else of any note, at least to me, shows up on that page.
So I tried looking up each of our domains (hudsonmarine.com, hmms-usa.com, hudsontrident.com, hudsonsystems.com, tmsalogix.com). Not a single one of these show any email detected in the SenderBase database.
So now I'm at a loss of where to look next. If I really do have a problem with one of my systems, I need more information to help me figure out which one as I have over 70 computers, most of which are laptops, and a dozen or more of which are spread around the world at any given moment.
And if the problem came about because of the Dell MessageOne service, then how do I figure out what happened so I can be sure it doesn't happen next time?
I'll do my best to answer questions in the hope the someone can point me in the right direction.