John Gruber and Mark Pilgrim are having a very public and very excellent conversation about Apple and file formats, proprietary and open.

Mark Pilgrim announced that he was switching from OS X to Ubuntu, citing the ever-advancing proprietary creep in Apple as the main reason for his switch. Apple “just doesn’t get it” when it comes to open file formats.

Uproar. Not least because of Pilgrim’s reputation as a long-standing Mac guru.

John Gruber responded to the post, arguing that “Apple gets it / Apple doesn’t get it” is too crude a view:

The question isn’t “Does Apple get it?”, but “Does Apple get it enough?” …. [W]hile it is easy to find ways to complain that Apple is not open enough — under-documented and undocumented security updates and system revisions, under-documented and undocumented file formats — it would be hard to argue with the premise that Apple today is more open than it has ever been before. (Exhibit A: the Web Kit project.)

But there are things that could be better, should be better, but aren’t, and it’s hard to ascribe these policies to anything other than management that is, at best, indifferent to issues related to openness.

Interesting as this all is (and there is a lot more of it—you should read the posts on both sites), I am posting this because it turns out that Mail.app played a crucial role in Pilgrim’s decision to switch.

In his response to John’s response, Mark writes that Mail 2.0 finally forced his decision to switch:

And then came Tiger, and Mail.app 2.0. In Mac OS X 10.4, Apple deliberately changed Mail.app to use their proprietary .emlx data format, apparently to work around the limitations of Spotlight. Mail.app 2.0 helpfully auto-converted all my wonderful mbox files into Apple’s shitty undocumented format. I’m now in the process of undoing the damage….

This was really the last straw for me. I was already feeling vaguely dissatisfied with Apple; now I feel actively betrayed. By the time I even realized what had happened (a year after buying OS X 10.4), it was too late. Now I’m forced to migrate all my mail yet again from yet another proprietary format, and the best documentation I’ve found so far is on LiveJournal. Jesus H. Christ, somebody deserves to be fired for that.