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The death of IP based reputation

Back in the dark ages of email delivery the only thing that really mattered to get your email into the inbox was having a good IP reputation. If your IP sent good mail most of the time, then that mail got into the inbox and all was well with the world. All that mattered was that good IP reputation. Even better for the people who wanted to game the system and get their spam into the inbox, there...

Weird mail problems today? Clear your DNS cache!

A number of sources are reporting this morning that there was a problem with some domains in the .com zone yesterday. These problems caused the DNS records of these domains to become corrupted. The records are now fixed. Some of the domains, however, had long TTLs. If a recursive resolver pulled the corrupted records, it could take up to 2 days for the new records to naturally age out. Folks can...

DNS, SERVFAIL, firewalls and Microsoft

When you look up a host name, a mailserver or anything else there are three types of reply you can get. The way they’re described varies from tool to tool, but they’re most commonly referred to using the messages dig returns – NXDOMAIN, NOERROR and SERVFAIL. NXDOMAIN is the simplest – it means that there’s no DNS record that matches your query (or any other query for...

Maybe the sky is only falling a little bit

There was quite a bit of breathless reporting last week about the DoS against Spamhaus and how it was large enough to break the Internet. As the postmortem has gone on, a few things are becoming clear. There was a lot of traffic, enough to swamp some major transit points. Most people, particularly in the US, saw no problems. Network engineers had more than a few sleepless nights trying to route...

Internet Storm Center on the Spamhaus DOS

The Internet Storm Center (ISC) has a blog post up discussing the DOS attack against Spamhaus. They do confirm they saw traffic approaching 300Gbps against Spamhaus. They also point out that most people probably never knew. The attack was significant, but not globally so despite the media reports to the contrary. When news of the attack reached the Internet Storm Center, we did have a brief...

More on the attack against Spamhaus and how you can help

While much of the attack against Spamhaus has been mitigated and their services and websites are currently up, the attack is still ongoing.  This is the biggest denial of service attack in history, with as much as 300 gigabits per second hitting Spamhaus servers and their upstream links. This traffic is so massive, that it’s actually affecting the Internet and web surfers in some parts of...

Troubleshooting tools

There have been a number of comments on my post about Hotmail moving to SPF authentication having to do with troubleshooting authentication failures. I have been helping clients troubleshoot these issues, and am able to take on new clients to solve authentication problems. Contact me for more information. Of course, many of these issues can be solved with access to the right tools. Steve’s...

MAAWG presents the first J.D. Falk award

Last week at MAAWG went much like all MAAWG conferences go: too much to do, too many interesting panels to attend, too many people to connect and work with, a plethora of very interesting keynote speakers and a total lack of sleep. Most of what happens at MAAWG is not public, but some of the events are. One of the things that I can talk about is the J.D. Falk award. This award was established by...

Setting up DNS for sending email

Email – and email filtering – makes a lot of use of DNS, and it’s fairly easy to miss something. Here are a few checklists to help: Data you need before you start: [table] Information,for example Return path / bounce address,bounces.myesp.com Mailserver hostname,mail4.myesp.com Mailserver external address,192.0.2.4 DKIM “d=”,greatbigmarketer.com DKIM selector,oct2012...

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