[pptp-server] firewall, pppd options, callback

[CB]

hi

is it possible to put MS-like callback options to the pppd?
my isp is banning pptp connections, so i have to stay with old 
fashioned dial modems to test poptop.

or does anybody have a clou to trick out my isp's firewall. i can 
connect to my poptop server but a few seconds later it's being 
rejected due to an error. poptop IS well configured, that's for sure. 

CB