[otrs] PostmasterFilter: Regexp not working

Hello, we are using the postmaster filter very excessively (having more than 100). Some regexp are really not failure-proof. But I thought this one (looking at subject line) is: ---8< --- (\D|^)123_Cust(\D|$)|(\D|^)123(\D).*(\D)Cust(\D|$) ---8< --- Why does this not match on ---8< --- Subject: 123: GPW Cust Lieferung /UPS hat Pal. gezogen **CUT OFF RELEVANT** ---8< --- ?! It should as per http://www.regexplanet.com/simple/index.html ... Are there some OTRS-specific limitations on Regexp?! Regards Jan Dreyer