On Sat, 5 Dec 1998, Alexander Langer wrote:
I know it is a little offtopic, but I wonder, why all my local mails
get an X-UIDL Header added.
I don't know if procmail does this or my sendmail.
X-UIDL is normally added by a POP3 server such as qpopper; UWwash's imapd
(and possibly also ipopd, I've never used that) adds X-UID.
So: What is this header for?
UID is "unique identifier". The L on the end comes from the POP3 command
UIDL, which means "unique identifier listing," the command to retrieve the
unique identifiers of a set of messages.
Some POP3 clients implement a crude form of remote mailbox synchronization
by using these UIDs.