[EXIM] return-receipt not supported?

Hi there,
I found nothing in the specification about this feature:

When I activate "return receipt" for example in Netscape Mailbox
sending options, then I get an error message from exim... something
like "not supported". I could not find any error or reject lines in the
logfiles.
Is this by reason, can I activate it to get delivery confirmations?

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M a r k   S e u f f e r t                         captain@???
Pirates Communication    Software + Internet   http://www.pirate.de
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*** Exim information can be found at http://www.exim.org/ ***