Vacation cleanup MTA option

Autoresponse periodicity MTA options:  (non-negative integer)
The  MTA option sets a modulus for the frequency at which per-user per-response vacation files are  "cleaned up",  (that is, scanned and expired entries removed). Each time one of the per-user per-response vacation files is opened (those files specified via the   MTA option), the value of the current time in seconds modulo the   value is computed. If the result is zero, then the file is scanned and all expired entries are removed. The default value for the option is 200, which means that there is a 1 in 200 chance that a cleanup pass will be performed.

See also:
 * Autoresponse periodicity MTA options
 * vacation_template MTA Option
 * Sieve vacation extension