Vacation hash algorithm MTA option

Autoresponse periodicity MTA options:  (hash algorithm name)
The  MTA option controls what hash algorithm the MTA uses to generate the names for vacation database entries. The value should be a hash algorithm supported by the MTA, one of MD2, MD4, MD5, SHA1, SHA256, SHA512, MD128, or MD160. The default if this option is not specified is to use MD4 for hashing the autoreply attributes and MD5 to rehash the name if it is too long. Note that the setting of this option must be the same across a deployment for successful coordination of vacation responses across hosts.

See also:
 * Sieve vacation extension