This keyword limits the number of postings that may be processed by the list in a calendar day (midnight to midnight, server time), and, with the addition of a (new) optional second parameter, limits the number of postings that may be accepted from any individual user per calendar day (midnight to midnight in the server's local time zone).
The default is Daily-Threshold= 50. When the value of the first parameter is reached, the list is automatically placed on hold, and the list owner or LISTSERV maintainer must issue the FREE listname command. Note that it may or may not be advisable to increase this parameter for higher-volume lists – individual list owners should study the issue carefully before increasing the daily threshold of their high-volume lists.
When the value of the optional second parameter is reached by an individual user, the user is told that their posting will not be processed and that they should resend it later if they still want it to be posted. The list itself is not held in this situation. The default is to have no such limit, in which case the second parameter is not defined. Note that list owners and list editors are exempt from the individual daily limit. There is no command to reset the limit for an individual user, although the list owner may update the header to increase the value.