From rfc4519:

2.26. 'preferredDeliveryMethod'#

The 'preferredDeliveryMethod' attribute type contains an indication of the preferred method of getting a message to the object. (Source: X.520)

( NAME 'preferredDeliveryMethod' SYNTAX SINGLE-VALUE ) refers to the Delivery Method syntax http://tools.ietf.org/html/RFC4517/.


If the mhs-delivery Delivery Method is preferred over telephone-delivery, which is preferred over all other methods, the value would be: "mhs $ telephone".

More Information#

There might be more information for this subject on one of the following:
[#1] - http://tools.ietf.org/html/rfc4519#section-2.26