Directories play an important role in aiding a site’s web visibility. Crawler-based search engines will, upon finding your site on a directory, or series of directories, consider these directories as one-way links. This will then add importance to your site’s relevance in “eyes” of these search engines and will most likely increase chances of your site being added to their listings.
Relevant reciprocal link exchanges are given some importance by search engines but most valued links, those which are most likely to boost a sites rankings in major SES are one-way links - sites that accept your link without requiring a reciprocal link from you. These links are highly regarded due to reasoning that other sites must hold your site in high enough esteem that having your link on their site is acceptable without an exchange requirement. Consequently, more one-way links, better!
Few, if any, sites today will agree to a one-way link favoring your site. The only way to achieve this is thru submitting to web directories.
Web directories and search engines have made a conscious effort to exclude bulk submitters. You’ve seen ads - “We submit to 1,500 search engines and directories for $10.00, etc.” For this reason, many directories require your registration and possibly entering a security code. Practically all of these directories require you provide an email address. Although hot mail or gmail is usually accepted, some directories will require an email corresponding to your domain name and will allow you to submit your site only after verification so it is best to establish an email specifically for web submissions.