Get the message? If not, it may not be your fault.

Microsoft Exchange engineers have always come under fire when a message that was sent to someone in their organization didn't get delivered, for whatever the reason may be.  The same goes for messages that bounce back for no apparent reason.  It could be a problem with the user's account (disabled, misspelled, etc) or it could be a problem with the server (offline, not connected to the net, etc).  It could also be a problem totally outside your organization, and that's what I'd like to talk about today.

In this ever-more interconnected world, routing of email can often depend more on external factors than internal ones.  Email messages can get mis-routed or even totally lost well before they reach your system, or can get purposely removed from the Internet somewhere along the way through no fault of your own.  If you're finding that more and more outgoing email is lost without any visible reason, the most common problem that is beyond your immediate control is getting accidentally blacklisted.

Blacklists are specific shared lists of either email servers or - in some cases - individual email addresses that spam control companies make available to end-users.  The most common of these is the DNS BlackList (DNSBL) which can either track IP addresses of servers known (or thought to be known) to send spam, or can track the domain names of such servers.  You can find out more about DNS BlackLists from Wikipedia at this link.  These systems collect information on servers and domains that send out spam and/or dangerous files (like viruses), and share that information with anti-malware companies (like McAfee and Kaspersky among others).  The anti-malware companies then use those lists to update their anti-spam and anti-virus solutions to protect consumers.

So if your server's IP address or domain accidentally ends up on these lists, suddenly external servers won't send mail to your servers anymore and won't accept incoming mail from you either.  It isn't easy to get on these lists by accident, but it could happen to you.  One or more internal users may get hit with a virus that sends tons of spam mails out from your email server, or someone totally outside your sphere of influence gets their computer taken over by a virus that forges headers to make it look like your servers are sending spam - and that's just two examples of things that could get you accidentally listed.

Once you're on these lists, it can be a very time-consuming process to get yourself un-listed.  Generally speaking, it will be a manual process of contacting each organization that has you listed on their blacklist system, and proving that you don't deserve to be there.  You can start your search at w3dt.net, which will assist you in figuring out which companies and filters have got your IP listed as up to no good.  Once you have that information, contact those organizations directly and either ask what caused you to get blacklisted or - if you already know that info - what you've done to stop the problem.

Be prepared to show that you identified who was sending the spam and why (and that you stopped it), or that you've isolated and removed the virus.  You will need to be patient and persistent, and will probably need to make several calls over a significant period of time (days to even weeks) to make sure that the problem gets solved.  Each organization that has you blacklisted will want their own proof that you're not a threat anymore, and in reality - provided they're not abusing their power - I can understand why they're being so careful.  Spam and viruses are a huge problem in the net today, and making sure they protect their clients is their business model.

Once you have the blacklist fixed to show you're not a spammer anymore, it can still take several days or longer for end-users of those services to get the updates to their spam and virus control systems.  So, if you do end up on a blacklist, you have quite a road ahead of you, but well worth it to clear your good name!

Getting blacklisted accidentally is a horrible thing.  Blacklists are a good thing overall for the benefit of email users all over the world, but when they suddenly stop you from emailing anyone (or getting email yourself), they can be a giant headache that you'll have to deal with effectively to get back in business.