Category Archives: Computing

Hardware, software, computer science and the rest

World IPv6 Day

Today is World IPv6 Day where a lot of major websites like Google or Facebook finally support IPv6 access for everyone. Unfortunately they plan to turn IPv6 access off tomorrow. 🙁

Well, this blog supports IPv6 since its creation. And I don’t have any plans to turn IPv6 access off. Oh, before I forget. Some people hid easter eggs in their IPv6 address:

> host -t aaaa has IPv6 address 2620::1c18:0:face:b00c:0:1

> host -t aaaa has IPv6 address 2001:420:80:1:c:15c0:d06:f00d

No Innovation for the Innovation Centre

My home is close to the Cambridge Science Park, a local business park where a lot of innovative companies have offices, including my employer.

There is also a telephone exchange called Science Park nearby which provides telephone and Internet services to companies at the Science Park and also to my home. But it is not innovative at all. British Telecom made the last upgrade to this exchange more than five years ago.

Well, I suppose I should take this opportunity to thank BT for their modern broadband network and outstanding support of innovation here in Cambridge.

Postfix and Dovecot: a Perfect Combination

Over a year ago I replaced Sendmail with Postfix on my main mail server. The new mail setup has worked very well ever since. There was however still room for improvement:

  1. I still used UW IMAP as the IMAP and POP3 server. This software works fine in general but is neither particular fast nor under active development anymore.
  2. As the Postfix binaries distributed with NetBSD don’t support SMTP Authentication out of the box my end users had to use my home grown mini SMTP server (listening on port 587) to send e-mails. This setup unfortunately made configuring e-mail client software more complicated and didn’t support STARTTLS for encrypting outgoing e-mail.

A week ago I decided to try out Dovecot. Dovecot is a secure IMAP and POP3 server for UNIX-like operating systems. In addition it can also serve as an authentication backend which adds support for SMTP Authentication to Postfix. After reading the excellent documentation in the Dovecot Wiki it took me only an hour to install Dovecot via pkgsrc , configure it and hook it up to Postfix. My system now supported SMTP Authentication and STARTTLS on both port 25 and 587.

Encouraged by this easy success I migrated the IMAP and POP3 services to Dovecot as well on the following day. I simply changed the Dovecot configuration as suggested in the migration instructions, turned off the old services, reloaded Dovecot and everything worked fine immediately.

My new setup still works reliable and fast after more than a week of service. The only compatibility problem was caused by a user who tried to use an uppercase account name. The old IMAP server had silently converted account names to lower case. Dovecot however needs to be explicitly configured to behave in this way.

Overall I can highly recommend the combination of Postfix and Dovecot. You get a fully-fleged e-mail solution with complete encryption support, a single user database and very good performance.