Hello everybody.

The following giagram describes how the two mail servers processes POP load balancing of Courier-IMAP(3.0.8).

-------------------------------------------------------------------- 　　　　　　　｜　　　　　　　　 　　｜ | 　　　　Load balancer(CSS)　　 OpenLDAP Server Client 　　　　　｜　　　｜ MailSpoolA　 　MailSpoolB 　　　｜　　　　　　　｜ 　　　｜　　　　　　　｜ 　　　 ------NFS-------

To explain the flow of the data, first, client establishes POP connection to the virtual address of loadbalancer to retreaves their email.

The loadbalancer uses "round robin" method, which decision relise on the sender's IP addresses.

Nornally, this works with no issues, however, on OutLookExpress(6) with "make copy of email on server" option enabled, within 2-5 days later, clients are receiving same email that they've already received in past 2-5 days.

Folowing is the result of IMAP's UIDL command:

*********************************************************** ■MailSpoolA [root@MailSpoolB root]# telnet localhost 110 Trying 127.0.0.1... Connected to localhost.localdomain (127.0.0.1). Escape character is '^]'. +OK Hello there. user ho...@example.com +OK Password required. pass ***** +OK logged in. list +OK POP3 clients that break here, they violate STD53. 1 11120 2 11370 3 1328 . uidl +OK 1 1196222123.16414.pop02.example.com,S=10855 2 1196248456.26392.pop03.example.com,S=11101 3 1196248477.26870.pop02.example.com,S=1299 . ■MailSpoolB [root@MailSpoolB root]# telnet localhost 110 Trying 127.0.0.1... Connected to localhost.localdomain (127.0.0.1). Escape character is '^]'. +OK Hello there. user ho...@example.com +OK Password required. pass ***** +OK logged in. list +OK POP3 clients that break here, they violate STD53. 1 11120 2 11370 3 1328 . uidl +OK 1 UID147-1195179386 2 UID148-1195179386 3 UID149-1195179386 . ***********************************************************

The values presented with UIDL command does not matches to one another. Can you tell us which value is correct, and are there any suggesion on how to avoid this issue from being occuring?

■System implemented with: RedHat ES 4(U4) Courier-IMAP 3.0.8 qmail-1.03

Thank you for your time to look in to this issue.