UIDL

UIDL

[François Pinard]

Hi, people.  I often noticed things like:

   X-UIDL: 3f52d1362f2c1d57ae074fac92f7c9a0

Would someone be kind enough to explain what it is, and why it is there?

-- 
François Pinard                            mailto:pinard@iro.umontreal.ca
Join the free Translation Project!    http://www.iro.umontreal.ca/~pinard

Re: UIDL

[Colin Rafferty]

François Pinard writes:

> Hi, people.  I often noticed things like:

>    X-UIDL: 3f52d1362f2c1d57ae074fac92f7c9a0

> Would someone be kind enough to explain what it is, and why it is there?

I have only ever seen it on spam.  I think that it is an artifact of a 
particular brand of spam-mailer software.

I find it very handy, since one of my first split rules is this:

        ("x-uidl" ".+" junk)

Do you ever get that header from a real mail message?

-- 
Colin

Re: UIDL

[Edward J. Sabol]

Excerpts from [ding]: (18-Mar-99) UIDL by =?ISO-8859-1?Q?Fran=E7ois Pinard?=
> Hi, people. I often noticed things like:
>
>    X-UIDL: 3f52d1362f2c1d57ae074fac92f7c9a0
>
> Would someone be kind enough to explain what it is, and why it is there?

It's a non-standard header inserted by certain POP3 or POP4 servers as a
method of storing the information for the `UIDL' POP command. It's like a
Message-ID basically. Unfortunately, when the client downloads the e-mail
from one of these servers, the e-mail still contains this `X-UIDL:' header.
There are at least two known POP servers which do this. The most common of
these POP servers will use exactly 32 hexadecimal digits as the value for the
`X-UIDL:' header. An example of which is quoted above.

A lot of spam, especially from about a year ago or so, was being sent out
with `X-UIDL:' headers. I think the intention was to fool these POP servers
into displaying the spam e-mails at the top of the recipient's inbox or
something like that.

Assuming you don't receive your e-mail from a POP server which inserts an
`X-UIDL:' header (and doesn't strip this header from the e-mail when
downloading it to your client), then you can definitely treat any e-mail with
an `X-UIDL:' header as spam *unless* it was `Resent-To:' you. That's an
important part caveat. If someone who does get his e-mail from a POP server
which inserts these `X-UIDL:' headers resends an e-mail to you or to a
mailing list that you subscribe to, then that valid, non-spam e-mail will
have an `X-UIDL:' header.

Later,
Ed

Re: UIDL

[Florian Weimer]

Colin Rafferty <craffert@ms.com> writes:

> >    X-UIDL: 3f52d1362f2c1d57ae074fac92f7c9a0

> Do you ever get that header from a real mail message?

I think some POP3 server made by Qualcomm adds it, but I'm not sure.
Of course, you won't see that header unless you get your mail from such
a server.

Re: UIDL

[Zlatko Calusic]

Florian Weimer <fw@cygnus.stuttgart.netsurf.de> writes:

> Colin Rafferty <craffert@ms.com> writes:
> 
> > >    X-UIDL: 3f52d1362f2c1d57ae074fac92f7c9a0
> 
> > Do you ever get that header from a real mail message?
> 
> I think some POP3 server made by Qualcomm adds it, but I'm not sure.
> Of course, you won't see that header unless you get your mail from such
> a server.
> 
> 

Exactly.

It is some kind of unique message identifier, by which pop daemon
probably takes care which messages it already transported, and which
are to be fetched.

I have it on every message I get (with fetchmail talking to remote
qualcomm popper).
-- 
Zlatko

Re: UIDL

[Hallvard B Furuseth]

Colin Rafferty <craffert@ms.com> writes:
> I find it very handy, since one of my first split rules is this:
> 
>         ("x-uidl" ".+" junk)
> 
> Do you ever get that header from a real mail message?

A few recent messages from the IETF srvloc group to IETF-Announce had
x-uidl, but that stopped -- I guess someone warned them that spam
filters killed those messages.

-- 
Hallvard