I found it myself!
I mistyped "DS:mailhost". It must of course read "DSmailhost".
Heiko Weber schrieb:
> Hi all,
> I just set up one of our AIX boxes to send SMTP mail through
> a relay host. It works, mail gets delivered to receiver on a
> remote box - BUT: the mail is also appended to "dead.letter"
> in my $HOME. Any ideas?
> With "mail -v" I see one message I can't explain:
> deliver: null host name in signature
> no match in Info Hider ... (needless to say). Is this something
> to care about? As I said: The mail gets delivered.
> When sending mail to local users or users at hosts that can be
> reached without the relay host no dead.letter occours.
> Thanks for any and all hints!
> I forgot: This is 4.2.1