Archive for the »Networking« Category

Why you should not use Microsoft live/hotmail/

August 2, 2014 - 2:36 pm

Subtitle: The new bussiness model of freemail hosters.
How can you make money from free e-mail?
Easy: Charge Admins for getting their mails delivered.

If you are not interested in my story, just skip to the most important part at the end.

Months ago Microsoft decided to classify mail from my server as spam and did not deliver it to the inbox of their freemail services like,,, … This was even before I migrated to my new system with IPv6 (OK Microsoft doesn’t care) and another V4 IP. I even tried with both machines and the same thing happend.

A few weeks ago now – suddenly – Microsofts’ servers started to bounc all my mails with the message: “Please contact your Internet service provider since part of their network is on our block list.” Of course I immediately checked public blacklisting services to see if my IP is listed somewhere – but nothing. All the other big providers also worked fine.

I double-checked their guidelines such as that reverse DNS and SPF must be configured properly, but everything was fine.
So I finally decided to open a ticket to ask to remove me from the blacklist. They in fact did this “for conditional mitigation” as they wrote and now I’m back to normal: Mails are delivered to the spam folder.


Category: Networking  No Comments »

Google is talking IPv6 to me.

February 13, 2014 - 3:38 am

We’re getting there!
It has been a while since I started digging into IPv6. My home network is running on IPv6 for a while, but now I’m confident enough to implement it in my productive setup.

My mailserver has now been fully migrated to IPv6 and while doing this I properly implemented TLS (with a CACert signed certificate) including perfect forward secrecy (PFS) and so on.

Here is how servers of major freemail providers are reacting to my new setup.

Provider sending to… receiving from…
GMail yes yes yes yes
GMX no yes no yes no yes no yes
T-Online no yes (no PFS) no yes
Yahoo no broken* (untested) (untested) no no no no
Apple no no no no

* Certificate does not match hostname. They are trying to use a wildcard certificate across two levels of subdomains which is forbidden for HTTPS and not explicitely allowed for SMTP.


Category: Networking  No Comments »

IPv6 and the ignorance of hosters

November 5, 2013 - 3:48 pm

A few weeks ago I received an e-Mail from a German server hosting company.  They told me about their completely renewed product range which now has the best cost-benefit ratio in the world. I remember that I got in contact with them years ago but then decided to rent my server from another provider.

OK, the e-Mail sounded extremely marketing oriented and so does their website.
But since the offerings looked quite reasonable I decided to give them a chance and replied with a list of technical questions.

One of them was about the size of the IPv6 subnet they are going to assign me. I was a bit confused that I couldn’t find anything about IPv6 at all on their website.

The answer came a few days later. I somehow expected it even though I never really believed that a root-server hoster could ever afford this kind of ignorance. But here it is (translated from German):

Indeed we do not YET offer IPv6 but it is already on our road map. This means it will be realized for you in the very near future.

It’s obvious what that means.

I didn’t answer back and haven’t heard from them, either. No, not quite. In fact I received another generated mail informing me that my very special and not transferable offer will only last until end of October. It seems the only thing they really renewed was their marketing department.

I wonder what’s going to happen in the next months and years. I suspect this is not the only provider ignoring IPv6.

Category: Networking  No Comments »

IPv6: First steps and experiences

October 21, 2012 - 7:21 pm

I’ve read and heard a lot about IPv6 in the last months, but wasn’t able to gain some practical experience yet.

No I finally found some time to get my hands on a simple IPv6 setup at home. Rather late for me as a network guy but actually I did it.
I’m running a Debian based router, which was routing my IPv4 for quite a long time. My goal was to add IPv6 routing so that my clients are able to use the “IPv6 internet”.

The setup was really easy. My main documentation sources were the Linux IPv6 HOWTO and an IPv6 with Debian tutorial.


Category: Linux, Networking  No Comments »