Defined in comm-central/ mailnews/ base/ public/ MailNewsTypes2.idl

typedef long nsMsgPriorityValue;

[scriptable, uuid(94C0D8D8-2045-11d3-8A8F-0060B0FC04D2)]
interface nsMsgPriority {
    const nsMsgPriorityValue notSet = 0;
    const nsMsgPriorityValue none = 1;
    const nsMsgPriorityValue lowest = 2;
    const nsMsgPriorityValue low = 3;
    const nsMsgPriorityValue normal = 4;
    const nsMsgPriorityValue high = 5;
    const nsMsgPriorityValue highest = 6;
    // the default for a priority picker
    const nsMsgPriorityValue Default = 4;
};