[otrs] Wrong customer ID at email ticket

Hello, I have setup a POP3 account to receive tickets by email... When I sent an email to that account from oneuser@domain, it arrives and is store at Raw queue... but the system show as customer ID anotheruser@domain... Why doesn't OTRS assign oneuser@domain as CusomterID for that ticket? Maybe I forgot to setup anything? Best regards M.A.