Can't send e-mails from contact page

I'm using the single contact. After filling out the form and clicking send I got the information box that the message has been send, no errors. But the mail don't drop into the admins mailbox, not in the spam-folder.

Joomla is set with phpmail

Any ideas where to look/check?

Hi,
Check your server, maybe phpmail function don't work on it.

Hi,

system mails from Joomla and RSFirewall are functional. phpmail seems to be working.

After some web research I found out that in the controller.php of com_contact there is an issue.

If I disable "if (!$pparams->get( 'custom_reply' ))" then the contact-form went through with PHP-Mail

Better than editing the php-code another user told me this: If the contact page is related to a Main menue item then you've to disable in the component parameters the last entry from YES (User defined) to NO. That works.

Are there any php-experts who can tell me more about this?