2 delivery failures for mail sent to the list

[Nigel Henry]

I've just sent, after working about 3hrs on it, a posting to the list on using 
Bogofilter with Kmail. Now. It's turned up in my inbox, so has obviously got 
to the list, but I've just checked mail again, and got 2 undeliverables in 
the unsure box referring to the mail I sent, but marked as being sent to 
other people. I only posted to the list, no CC's.

These are the places they were supposedly being sent.

alcoholclay(at)rotronix.co.nz
and was returned by
postmaster(at)rotronix.co.nz
and the returned message referred to was headed
Using Bogofilter with Kmail (my setup)

the 2nd one.

stephinebutch(at)spinefex.com.au
and was returned by
postmaster(at)spinefex.com.au
and the message referred to had the header changed to.
[SPAM]-Using Bogofilter with Kmail (my setup)-Bayesian Filter detected spam

All "@" have been changed to "(at)" by me.

Any suggestions as to what is going on here?

I can send the headers from my post which came back with the returned messages 
if necessary.

Nigel.