I installed qpopper-4.0.5 from source; configured it with the --disable-specialauth option and compiled, but I always have the following error when connecting to my mailbox:

-ERR [AUTH] Password supplied for "username" is incorrect

The error is the same regardless of whether I try to login via telnet or a mail client, and to what user account.
There is a delay of cca. 10 s before rejecting the request. (When I set the mail client to use encrypted authentication, the connection is rejected without delay)

I want qpopper to use /etc/passwd for authentication and let me in. Is it possible?

qpopper should be using /etc/passwd for authentication. Can you take a look at you system's maillog for qpopper errors? You might also want to check syslog (messages) for authentication errors. It might be a pam restriction that is in place.

I've compiled qpopper 4.0.5 many times before and have never seen this problem before... I prefer qpopper over the pop3 server from the imap server package because it is leaner.

I hope this helps, good luck.

/var/log/maillog does not contain any error messages but those of sendmail
/var/log/messages contains the same error message plus the following:
[AUTH] failed attempted login to username from host (cross.foo.bar) 192.168.226.3.

As for the pam restriction: can pam restrictions prevail even if I have the default installation?
I did not change the default configuration options except for using the --disable-specialauth option.

Pam restrictions can be placed on the qpopper completely isolated from the actual installation of qpopper itself. If you are running qpopper from xinetd, there could be a host restriction in the xinetd configuration... Without more information, I can't be sure.

You are right, I found an uncommented line applicable to pop3 in pam.conf.
I deleted that line, but qpopper still does not work.
I start qpopper from inetd. Is that the problem?

By the way: it should not be a pam failure; if it was, the error message would read '... PAM authentication failure ...' (I found a lot of these errors with google).

The qpopper README tells something about /etc/shadow. I do not have that file. Is that a problem?

It must be something trivial.

(Many struggle here with samba - for me it worked almost 'out of the box' - thought I am lucky - now s[u]{1}cking with qpopper...)

I compiled qpopper with the debug mode enabled.
Here is the log found after an unsuccessful connection:

Jul 25 10:49:59.006 2003 [4923] Trace and Debug destination is file "/var/log/poplog" [pop_init.c:888]
Jul 25 10:49:59.006 2003
Jul 25 10:49:59.016 2003 [4923] (v4.0.5) Servicing request from "cross.foo.bar" at 192.168.226.3 [pop_init.c:1186]
Jul 25 10:49:59.016 2003
Jul 25 10:49:59.016 2003 [4923] before TLS; tls_support==0 [popper.c:181]
Jul 25 10:49:59.016 2003
Jul 25 10:49:59.016 2003 [4923] Skipped TLS Init [popper.c:205]
Jul 25 10:49:59.016 2003
Jul 25 10:49:59.017 2003 [4923] (v4.0.5) Intro [popper.c:247]
Jul 25 10:49:59.017 2003
Jul 25 10:49:59.017 2003 [4923] +OK Qpopper (version 4.0.5) at pollux.foo.bar starting. [popper.c:260]
Jul 25 10:49:59.017 2003
Jul 25 10:49:59.018 2003 [4923] Qpopper ready for input from (null) at cross.foo.bar [192.168.226.3] [popper.c:294]
Jul 25 10:49:59.018 2003
Jul 25 10:49:59.021 2003 [4923] Received (10): "USER username" [pop_get_command.c:105]
Jul 25 10:49:59.021 2003
Jul 25 10:49:59.023 2003 [4923] home (15): '/usr/home/username' [pop_user.c:224]
Jul 25 10:49:59.023 2003
Jul 25 10:49:59.023 2003 [4923] +OK Password required for username. [pop_user.c:437]
Jul 25 10:49:59.023 2003
Jul 25 10:49:59.023 2003 [4923] user returned 1; CurrentState now auth2 [popper.c:338]
Jul 25 10:49:59.023 2003
Jul 25 10:49:59.024 2003 [4923] Qpopper ready for input from username at cross.foo.bar [192.168.226.3] [popper.c:294]
Jul 25 10:49:59.024 2003
Jul 25 10:49:59.025 2003 [4923] Received: "pass xxxxxxxxx" [pop_get_command.c:96]
Jul 25 10:49:59.025 2003
Jul 25 10:50:09.046 2003 [4923] username at cross.foo.bar (192.168.226.3): -ERR [AUTH] Password supplied for "username" is incorrect. [pop_pass.c:1230]
Jul 25 10:50:09.046 2003
Jul 25 10:50:09.047 2003 [4923] [AUTH] Failed attempted login to username from host (cross.foo.bar) 192.168.226.3 [pop_pass.c:1383]
Jul 25 10:50:09.047 2003
Jul 25 10:50:19.056 2003 [4923] pass returned 0; CurrentState now halt [popper.c:338]
Jul 25 10:50:19.056 2003
Jul 25 10:50:19.057 2003 [4923] +OK Pop server at pollux.foo.bar signing off. [popper.c:360]
Jul 25 10:50:19.057 2003
Jul 25 10:50:19.057 2003 [4923] (v4.0.5) Ending request from "username" at (cross.foo.bar) 192.168.226.3 [popper.c:378]

So you've got no /etc/shadow file? This is a pretty good indication that you're not using shadow passwords, so all your passwords are actually being stored in /etc/passwd (I think). This also means that you should compile qpopper with --disable-specialauth. I'm not sure what the default is, but if your not using shadow passwords, you'll want this disabled.
See botton of page 17: ftp://ftp.qualcomm.com/eudora/server...pper/GUIDE.pdf

There's no problem with running qpopper from xinetd, that's how I've always done it. It can be run standalone if compiled with --enable-standalone, but that's not a problem here. Just for giggles, what does your /etc/xinetd.d/popper file (or similar) contain?

Good luck!

Naturally I compiled qpopper with the --disable-specialauth option.

Also tried compilation with any combination of other options that might count and, doing all that with several qpopper versions, with the same result. (Just being over the 100th compilation...)

Today I begin my summer holliday, (the server is already shut down), so I cannot make any attempts or survey for two weeks.

Thanks for your kind attention!