Datefour, datetwo Channel Options

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Two or four digit date conversion (datefour, datetwo)

The original RFC 822 specification called for two digit years in the date fields in message headers. This was later changed to four digits by RFC 1123. However, some older mail systems cannot accommodate four digit dates. In addition, some newer mail systems can no longer tolerate two digit dates! (Please note that systems which cannot handle both formats are in violation of the standards.)

The datefour and datetwo options control the MTA's processing of the year field in message header dates. datefour, the default, instructs the MTA to expand all year fields to four digits. Two digit dates with a value less than 50 will have 2000 added while values greater than 50 will have 1900 added.

datetwoinstructs the MTA to remove the leading two digits from four digit dates. This is intended to provide compatibility with incompliant mail systems that require two digit dates; it should never be used for any other purpose.