whoa... a lot of questions ....
server is local (10.10.10.15) via a FW connected to the internet. Users connection from internal LAN. pop & smtp server in MS Outlook (express) is server ip-address (10.10.10.15) hostname is mail.dltmedia.nl. only the hostname (mail) replys on ping.
at this moment de mx points to another ip-address (provider) but we want to receive out e-mail on this new e-mail server.
Another thing is that some mail domains arent resolved. Getting undelivered msg see below
This is the Postfix program at host mail.dltmedia.nl.
I'm sorry to have to inform you that your message could not be
be delivered to one or more recipients. It's attached below.
For further assistance, please send mail to <postmaster>
If you do so, please include this problem report. You can
delete your own text from the attached returned message.
The Postfix program
<email@example.com>: [pinbizz.nl]: Name or service not known
but when i send an email from my other account (isp) then there's is no problem.