How to modify plesk qmail local delivery and/or add actions to it

when I try to implement other local delivery software for e.g. I need to modify .qmail file when a new email account is created/updated via plesk . if you just edit .qmail it will be rewrite on any email account update from plesk and same for new accounts you have to provision this shit somehow.

for example you can modify local delivery in .qmail to replace  “/usr/bin/deliverquota ./Maildir” with something like “/var/qmail/bin/preline -f /opt/libexec/dovecot/deliver -d user@domain”.

basically there are two ways to do that from plesk:

one is using event handlers: http://download1.swsoft.com/Plesk/Plesk8.6/Doc/en-US/plesk-8.6-unix-administrators-guide/22819.htm

second is using mail handlers: http://download1.parallels.com/Plesk/Plesk8.6/Doc/en-US/plesk-8.6-unix-mod-api/38611.htm