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?
You need to load the IPA file via iTunes.
As long as you have the correct device certificates in place when you created the IPA, you should be able to drag and drop the IPA to a connected device in iTunes.