AppleMail vs. sendmail

[Sytse Kuijk]

OS X server 10.2.5, AppleMail smtp server.

We have been using the AppleMail stuff since installation here some 
time ago. It works relatively well, but there is an annoying issue I 
do not seem able to resolve. I hope someone has experience around 
here with this sort of stuff.

There are certain addresses (hosts) that, when we send mail to it, 
the mail is returned with a non delivery message. When checking at 
low level (tcpdump) I see that for correctly working destinations, 
the mail is sent by the server immediately after receiving it on the 
server. For the not working destinations, the server does not even 
attempt to make a connection, it just sits on the mail for 4 hours, 
sends a warning to the sender, waits another 68 hours, and sends a 
non delivery message. Sounds to me that these addresses are damned by 
something in the AppleMail configuration (DNS settings?), so I wonder 
how I can reset all the tables etc. the AppleMail has.

One alternative is ditching AppleMail and using sendmail. Is that a 
better way to go? I never set that up, it is difficult to make it 
secure?

thanks,

sytse