strange pop protocol?

[Stefan Palme]

Hi all

Using the POP3 server of Cyrus IMAP Server 2.3.13 I can see the 
following POP3 protocol (sniffed via tcpdump and friends and 
obfuscated sensitive data):

----------------------------------------------------
+OK <98640940.1241005202 at imap.example.com> imap.example.com Cyrus POP3 v2.3.13-Gentoo server ready
USER username
+OK Name is a valid mailbox
PASS passphrase
+OK Mailbox locked and ready
UIDL
+OK unique-id listing follows
1 1157352258.220081
2 1157352258.220082
.
LIST
+OK scan listing follows
1 14363
2 360389
.
RETR 1
+OK Message follows
Return-Path: <sender at example.com>
Received: ...
/// here the email headers and body follow

RETR 2
DELE 1
DELE 2
QUIT
----------------------------------------------------

The point I am interested in is the fact, that both the UIDL and the LIST
commands show TWO mails. But when the client tries to retrieve the second
one (RETR 2), nothing is returned. 

This does not happen all the times - I've already seen non-empty "RETR 2"
calls during other client sessions.

Is this normal behaviour? Or do I have to afraid of mail loss, because after
the empty "RETR 2" the clients deletes BOTH messages from the server. Is this
strange message 2 really "not-existing", or do I loose some mail data anywhere?

Thanks and regards
-stefan-