This is set to 'Yes' for most organizations so that mail or packages can be addressed to a specific contact at a company. This allows company correspondence to be sent to the appropriate contact person, as well as allowing people to use their work address for publications or packages, for example.

If set to 'No', a company address will only have the company name, and a user address will only have the person's name.

If set to 'Yes', the number of available address lines is expanded from two to three. The extra address line makes it possible to store exceptionally long or complex addresses when needed. This extra address line is also handy when the addressee information takes up more than one line, although this requires some fudging. This use case most commonly applies to large institutions or companies with campuses, where the addressee data takes three lines: the contact name, the building or department, and the name of the company or institution. Since addressee information is actually part of the address, the building or department can be added to the Company Name addressee field without in any way affecting the value in the actual Company Name field. The third addressee line containing the name of the company or institution then occupies the first of the three address lines.

If set to 'No', this third address line will not be available.