lists(_at_)professional(_dot_)org writes:
...
3. Some POP clients (Netscape and Pegasus are two I know of) apparently
add this field as part of their stored message (you see it locally, but it
wasn't transmitted that way) -- it is a separatley requested/generated
header from the mail server (used to uniquely identify the message for
storage/retrieval purposes). I prefer the way Eudora handles it -- since
The X-UIDL: header is not added by the POP client but by the POP
server. Read rfc1939, the POP3 rfc, and you'll see that the server
must generate a unique ID for each message that is static across
connections to the pop server. The qpopper (and I think the Berkeley
popper) add the X-UIDL: header to the message as stored in the mailbox
to preserve the UIDL value across invocations.
Other pop servers, such as cucipop, don't do this, but generate the
UIDL in some other way (cucipop by md5ing the message), and thus don't
generate an X-UIDL: header.
the field IS NOT PART OF THE MESSAGE, it IS NOT STORED WITH THE MESSAGE.
This is server dependent.
...
messages on the server). In any event, this header shouldn't normally
appear in the message header when procmail gets it from sendmail -
excepting when it is spam, or somebody forwarding a message which has the
header inserted for no good reason.
If you use fetchmail to get your mail from a pop server that inserts
the X-UIDL: header, than every message you get will contain the X-UIDL:
header. However, this is a relatively rare set up, and You Know Who Are.
The rest of us can use it to filter spam.
Philip Guenther