RT sending each e-mail two times or

Hi.

I’ve just installed RT with qmail and PostgreSQL. Everything seems to work
fine, but everyone who gets an e-mail (e.g. the
OnCreate-AutoreplyToRequestors mail) from RT gets this mail two times, one of
which is a CC or a BCC.

I did not change any Scrib.

I don’t know where to look to solve this problem. Can you give me a hint?

TIA

Greetings,
Matthias