In Lion’s new Mail.app, is it possible to change the font size of the mailbox list

There are several ways to do that.

The easiest way would be to install a Plugin which formats outgoing E-Mail and give you the option to change specific characteristics to you liking (Font, Size etc.). For that you should look into the following Plugins:

1. MessageFont

   "WYSIWYG for your outgoing emails If Outlook for Mac, Thunderbird and other email apps can set the default composition font1, why can’t Apple Mail? With MessageFont, you can! MessageFont lets you set Apple Mail’s default composition font for new rich text outgoing messages. [...]"

2. Universal Mailer

   "Universal Mailer is a Mail.app plugin that solves some issues when sending emails. It removes ATT00001.htm files, it correctly formats messages with attachments and inline images and offers an option to set the default font for outgoing messages. [...]"

Another way would be to change the default Font Size via the Terminal, f.e. in 24, open up the Terminal and type in:

defaults write com.apple.mail MinimumHTMLFontSize 24

That will change the Font to 24pt, but that includes the Page you want to forward from Safari if you choose 'Webpage'. If you just forward the Link everything should be fine.

Use TinkerTool to change the System font.

Problem is, making larger System fonts can do wonky things not only in Chrome but other apps/windows. Other than trying diff font sizes, how can I adjust for this in Chrome? Maybe I can increase the address-bar height somehow - possibly by making larger extension icon sizes, or some other customization settings I've not yet found? Suggestions welcome.

The following shows an example of problems with System = 24:

(I'm the question author. Default System font size for my MacBook = 13.)