Version:           1.5.9 (using KDE 3.1.9)
Compiler:          gcc version 2.95.4 20020320 [FreeBSD]
OS:          FreeBSD (i386) release 4.9-PRERELEASE

For quite some time, KMail has failed to connect to my mail server, any combination of settings results in the error described above.  Watching from the mail server shows no hostname is sent with the EHLO, even if one is set specifically in KMail's configuration.

I can repeat this with a second mail server at another location, also running Exim.

The 'check what the server supports' dialog no longer works either, it takes quite a while to timeout, but then says it couldn't reach the server (which is local, on the LAN)

Recompiling with debug right now, but all I'm seeing on the console already is:
kdeinit: Got EXEC_NEW 'kio_smtp' from launcher.
kio (KLauncher): kio_smtp (pid 95761) up and running.
kio_smtp: S: 220 mandarin.fruitsalad.org ESMTP Exim 4.14 Mon, 22 Sep 2003 13:05:42 +0200
kio_smtp: C: <7 bytes>
kio_smtp: S: 501 Syntactically invalid EHLO argument(s)
kio_smtp: closing connection

The server does not reply with a multiline banner (yes, I did check for duplicates), 
telnet shows:
Trying 192.168.254.243...
Connected to mandarin.internal.hasta.se.
Escape character is '^]'.
220 mandarin.fruitsalad.org ESMTP Exim 4.14 Mon, 22 Sep 2003 12:56:55 +0200
EHLO kurant
250-mandarin.fruitsalad.org Hello kurant.internal.hasta.se [192.168.15.5]
250-SIZE 52428800
250-PIPELINING
250 HELP
HELP
214-Commands supported:

Mail is sent correctly from any other client I have available, and the server is in  production use, it is only KMail that is failing to speak to it.  I can probably arrange a test account on it if needed.