On this site, I found that you can distribute through email:
Ad Hoc Distribution
With Ad Hoc distribution you can share your app with up to 100 other iPad, iPhone, or iPod touch users. Through email or by posting it to a server, users can download and install your app.
I cannot find any instructions on how to do this. Since it says, "through email or by posting it to a server", I am expecting to be able to send an email with the needed file(s) attached without using a server. Is this possible?
I tried emailing myself the .ipa that results from archiving the app in Xcode, but it says:
Mail cannot open this attachment.
How can I distribute an app through email if the Mail app doesn't know what to do with it?