iPad can't connect to Lion mailserver

Hi all,

Yesterday I did a clean install of OS X Lion on my Mac Pro and installed Lion Server with it. Today I had time to setup the mailserver and everything went suprisingly easy.

I have set up the profile manager and mail (no SSL) and the Mail application on the Mac Pro was able to send and receive mail. The MacBook Pro from work was also able to send and receive using Mozilla Thunderbird, which was even easier to configure than Apple Mail. So far so good.

The problems started when connecting my iPad to the mailserver. Setup was a breeze and went without a hiccup (except for complaining about using no SSL). After confirming I really did not want to use SSL, it immediately started receiving mail, so everyting seemed ok. But when I try to send a mail from my iPad, it says sending mail for about 30 seconds and then gives a warning it failed to send the mail. After trying several options for security and all, I went to have a look in the server logs and they give me this:

24-07-11 17:06:32,832 postfix/postscreen: CONNECT from [xx.xx.xx.xx]:47137

24-07-11 17:06:32,832 postfix/postscreen: PASS OLD [xx.xx.xx.xx]:47137

24-07-11 17:06:32,833 postfix/smtpd: connect from xxxxxxx.upc-g.chello.nl[xx.xx.xx.xx]

24-07-11 17:07:03,192 postfix/smtpd: lost connection after UNKNOWN from xxxxxxx.upc-g.chello.nl[xx.xx.xx.xx]

24-07-11 17:07:03,192 postfix/smtpd: disconnect from xxxxxxx.upc-g.chello.nl[xx.xx.xx.xx]

24-07-11 17:07:03,197 postfix/postscreen: CONNECT from [xx.xx.xx.xx]:36506

24-07-11 17:07:03,197 postfix/postscreen: PASS OLD [xx.xx.xx.xx]:36506

24-07-11 17:07:03,199 postfix/smtpd: connect from xxxxxxx.upc-g.chello.nl[xx.xx.xx.xx]

24-07-11 17:07:33,604 postfix/smtpd: lost connection after UNKNOWN from xxxxxxx.upc-g.chello.nl[xx.xx.xx.xx]

24-07-11 17:07:33,604 postfix/smtpd: disconnect from xxxxxxx.upc-g.chello.nl[xx.xx.xx.xx]

Basically the iPad is connecting two times and both times it seems to send an invalid/unknown command (UNKNOWN), after which it drops connection.

How is this possible, why is one Apple product not able to talk to another? Does anyone know what is wrong? I'm just running a complete clean setup, I did not mess around in the postfix config files, so all settings done are done from the Server application downloaded from the AppStore.

Some info about versions:

Mac Pro: OS X 10.7 Lion with server

iPad: iOS 4.3.4

Thanks in advance!

Michael