Formatting Incoming Mail?

how can I get e-mail incoming messages to be listed in double space?

I don't know if things have improved even for outgoing, see:
http://www.mac-forums.com/forums/switcher-hangout/302785-formatting-email-double-spacing.html

so I sure don't know how one would do it easily and quickly with any incoming, especially with Mail and especially considering it doesn't even allow one to change anything on an incoming email.

Now, if we were still able to use Eudora with OS X after 10.6.8, that would be a simple matter, but alas, not gonna happen…

If you are asking whether incoming mail can be displayed automatically as double spaced I don't think so. My understanding is that the formatting of a message is set by the sender. Others may be better able to answer this.

Perhaps it can be done by Applescript but I don't see anything that looks like a relevant command.

Note: Thread title changed to something more descriptive. This may generate more answers.

You don't. The original formatting of the email is -- of course -- controlled by the sender. If you're having trouble reading incoming messages, you can hit option-+ (plus sign key) to make it bigger.