Is there are replacement for 'UIDL'?

I've just had an email from one of our users, which they've been sent by 
their ISP (British Telecom) which looks to me like total baloney (which 
wouldn't be unusual), but I just want to check that there's not something 
I've missed...

Anyone out there want to read through it, and tell me that I'm correct, or 
that I've missed something?

Basically, if you send their server a 'UIDL' command it gives you a set of 
IDs for the messages, then if you ask a few hours later, it'll give you a 
totally different set of IDs for the same messages. As far as I am 
concerned this is a breach of the relevant bits of RFC 1939.

Their response was:

BTInternet as was, now BTOpenworld, whose server actually holds my "real" 
mailbox acknowledge that changed UIDL's can be demonstrated [now with 
increasing frequency] BUT they say that their server does not add a UIDL AT 
ALL to any messages on their servers, they are using, instead, their own 
Unique Message ID [which does persist across sessions]. They say that this 
is acceptable under RFC POP3 supplemental extension rules and blame 
BTWebworld [the domain-forwarding source of most of my mail] for ?somehow 
attaching changeable UIDL's which are confusing VPOP3 [our mail software].


They seem to be saying that this 'Unique Message ID' is a replacement to 
the UIDL which they claim not to add to messages, but which their servers 
WILL give you if you send a UIDL command. I don't know what these 'RFC POP3 
supplemental extension rules' are that they're talking about.

The only thing I can think of which they could mean by 'Unique Message ID' 
is the 'Message-Id:' header line which is normally added by the message 
SENDER, not POP3 server, and which isn't *guaranteed* unique as a UIDL is. 
Also, it's not generally a usable replacement for UIDL since there's no 
quick way of getting it.

Is there anything I've missed, or is it just waffle from an ISP which 
doesn't know what it's talking about?

I don't see what's hard about assigning a constant UIDL to each message. 
And if they really find it as difficult as they seem to, surely they should 
simply not implement the UIDL command at all - after all it's optional.

Paul				VPOP3 - Internet Email Server/Gateway
[email protected]			http://www.pscs.co.uk/