A follow-up letter is often written during the early stages of a relationship and therefore the writing style needs to be fairly formal. At the same time, it is aimed at people, so it should have a distinctly human touch. So, the trick is in the balance of personal and professional.... Now if you write a post that has both internal links to your site and external links to other sites, then you probably want to get the maximum link juice to your internal posts. You can do this by adding a nofollow attribute to your external links.
If you haven't added a Nofollow to the tag, however, search engines will still follow all the links on the page. In other words, the page will be read by search engines but it won't be indexed. If you don't want search engines to follow links on your page you need to add a Nofollow to the command.