Name: popexpiretime
Type: DURATION
Default-Value: -1
Last-Modified: 3.1.8

The duration advertised as being the minimum a message may be left on the
POP server before it is deleted (via the CAPA command, defined in the POP3
Extension Mechanism, which some clients may support).  This duration has a
granularity of whole days, with partial days truncated (so e.g. "45m" is
effectively "0d").  "NEVER", the default, may be specified with a negative
number.

The Cyrus POP3 server never deletes mail, no matter what the value of this
parameter is.  However, if a site implements a less liberal policy, it
needs to change this parameter accordingly.

For backward compatibility, if no unit is specified, days is assumed.
