In web pages, web and email addresses are usually hidden from view behind hyperlinks, so they don’t cause typographic trouble.
But in print, web addresses present two problems.
The first problem: web addresses can be long. Really, really long. Running the whole web address may be fine if you can bury it in a footnote. But it’s useless if you’re hoping readers will type the address on their own.
For a more usable web address, use an address-shortening service like TinyURL or Bitly. These services take a web address of any length and convert it into a short address like http://tinyurl.com/p5wf3c. This is easier to read and type. But it doesn’t reveal the underlying web address. It also isn’t guaranteed to work permanently.
If you put a web address in a footnote or endnote, consider running the long version with a shortened version next to it. Then you’re covered. For instance:
8825768d0067b375?OpenDocument, also available at http://tinyurl.com/y6o4yte.
The second problem: web addresses are difficult to wrap onto multiple lines. A web address is one unbroken string of characters. You don’t want your web address hyphenated, because readers will likely mistake the hyphens for part of the address. Therefore, use hard line breaks to set the points where the web address should wrap onto the next line.
Email addresses are shorter than web addresses and thus not as painful. But they shouldn’t be hyphenated either, for the same reasons.
Word processors have an annoying default habit of making every web and email address underlined and blue. That might make some sense if you’re creating a PDF that needs to include hyperlinks. But it makes no sense at all if you’re creating a document that needs to be printed.
What about typography within emails? Your options are limited. Unlike a PDF, fonts don’t get transmitted with an email. So even though you can compose an email in any font you like, recipients won’t see that font unless they also happen to have it installed. Moreover, recipients read email on a variety of devices, which have different and unpredictable typographic capabilities. My policy: treat email as a typography-free zone.