[imp] IMP using sendmail, not executable...

[Doms Pieter]

I'm forced to use the sendmail option, because the smtp-server isn't open relay! So I tried sendmail, but it has been integrated with qmail... 

I always get the same error, when i hit the send-button:
There was an error sending your message: sendmail [/usr/lib/sendmail] not executable

I reviewed this with the admin of the server, but he did not find the solution either... If you know something, pls mail me back!

Greetz

Doms Pieter