[Users] snom registration expiry

Hello! I've been running my experimental(production in the near future) environment with ser and a mysql-db for some months now but want to switch to postgres and openser soon. i'm using a very simple routing as i didn't have the time to dig deeper into the ser-routing-language. i've already adapted my current config-file to openser and the routing works as expected. still, there is one major problem i could not cope with yet: Expiry. i'm using a snom 190 and had the "proposed expiry" set to 10min with ser, without any registration-problems or registration-loss. with openser with the same settings on the snom i loose my registration within a few minutes after phone-reboot, when setting "proposed expiry" to 1min on the snom it works without problems endlessly - but setting this generally to 1min on all the phones that will register at openser doesn't seem to be a good idea and i guess there are other ways. I've tried to force it with the modparams min_expire 100, max_expire 1800 and default_expire 600 but the result is still the same, calls are possible after rebooting the phone, but after some minutes(below 10min), i loose registration. I had similar problems due to a firewall closing the connection, but that occured when i had set a 60min expiry on the snom(with ser), the 10min timeout works fine with the same snom 190 and ser. I've searched a lot for expiry-problems but only found the modparams above that could be responsible for this. Sorry if my explanations sound simple and untechnical, but i'm pretty unexperienced with ser/openser yet so i try to explain it the way i understand it, simple ;-) i've attached my config-files, both ser and openser: 21X.XXX.XXX.100 is the host running ser(port 5060) and openser(port 5061) 21X.XXX.XXX.101 is asterisk1 21X.XXX.XXX.102 is asterisk2(asterisk2.de.domain.cc) i'm registering my phones at openser with the domain siptest1.domain.cc, the second domain sip2.de.domain.cc is a test for a multidomain setup but doesn't work yet(i can't use the domain-column provided by the db since i need two different origination domains in asterisk's sip.conf to seperate the calls - maybe not the best approach...) p.s.: a second question regarding the multidomain - i can't register with sip2.de.domain.cc - i guess there's something wrong with my regexp "if (uri=~"^sip:(.+@)?((sip2\.)?(de\.)?domain\.cc)([:;\?].*)?$") {" someone having mercy and tell me what is wrong with my syntax(or maybe a link to a descriptive documentation - ser admin guide was not enough for me)?