PHP mail() sometime work sometime don't

[wonski]

I'm also having problem with the PHP mail() function.

Its sometime can sent, sometime can't and return the following error:

PHP Warning: mail(): Could not execute mail delivery program '/usr/sbin/sendmail -t -i'

The permission of that sendmail link is:

0 lrwxrwxrwx 1 root root 23 Oct 20 2005 /usr/sbin/sendmail -> /var/qmail/bin/sendmail

and permission for /var/qmail/bin/sendmail is:

12 -r-xr-xr-x 1 root qmail 9640 Aug 24 2005 /var/qmail/bin/sendmai

My /var/qmail/control/me file is correct, as it can sent out sometime.

Other servers which also with Plesk are alright. Only this particular server having the problem. Anyone know what could be the problem? Is that the setting or permission?

Thanks in advance

Wonski