I am trying to run sendmail in tandem with qmail. Presently there is a symlink in the /usr/sbin/ directory pointing to the /var/qmail/sendmail binary. What do I have to change in the qmail configuration if I remove the symlink and rename sendmail.sendmail (I think this is the present name for sendmail's binary) to sendmail so my program can call it. What do I have to do to isolate the two installations aside from selecting a different port in sendmail's configuration?
The sendmail symlink is only provided to provide a sendmail-like interface to qmail, so 3rd party programs that expect sendmail. Qmail itself doesn't depend on it and should never call it.
Renaming/replacing it with a real sendmail binary should not affect qmail - it just means any 3rd party programs that call it will now be interacting with sendmail and not qmail.