Error "Error Could not instantiate mail function." on vendor contact only

[Mojo78]

Hello,
following problem:
Virtuemart Vendor-Contact Form does not send e-mails anymore, i believe since i updated to VM 2.0.24 some 2 or 4 weeks ago, but im not sure. The funny thing is: order confirmation-mails, account-creation mails and so on do work! So it should not be a Joomla or a hoster-problem.

Error message is: "Could not instantiate mail function."

Current Version:
VM 2.0.24c
Joomla! 2.5.16

Mailer: phpmail

I tried disabling my template but this doesn't work, too. On my development-xampp-host no PHP-Warnings / Errors  / Notices are shown. it doesnt send Mails (mail-server not configured) but thows no errors. I checked server logs and found nothing. Perhaps someone here has an idea?

Bye, Mojo

[sandstorm]

Hey Mojo, I'm not sure this is a virtuemart issue?
Check out this http://forum.joomla.org/viewtopic.php?t=803325 and see if it helps you out.

[jenkinhill]

If you are logged into the FE as superuser/vendor or use that email address as the from address then some servers (not all) will reject the mail as from and to addresses are identical.

[Mojo78]

thank you for your answers!
@jenkinhill: i wasn't logged in FE when testing. the vendor-contact-form didn't work for our clients too.
@sandstorm: i believe it can't be a joomla problem, because i had no general mailing problem - just in the vm-vendor-contact-form - even with std-template. btw safe mode is off.

yesterday in the night i tested on my local xampp (1on1 copy of life-page), and checked the variables down to the php- mail() function:
All parameters are filled like i would expect it. everything ok - on xampp @mail() does return true (which means everything is OK).
I absolutely do not understand whats the problem and can't debug on life server. this would be a perfect x-files episode.

So since today in the afternoon I use com_contact. It works flawless.

Bye, mojo