PHP.INI and PEAR::SOAP remote calls problem

Hi It seems that there is an issue about the php.ini constants and PEAR::SOAP remote calls. A simple call to the php 'mail()' function won't work and the reason returned in the soap fault is the classic "SMTP server response: 553 sorry, that domain isn't in my list of allowed rcpthosts". At this point you would tell me to check the php.ini file for the "SMTP = ..." line, but this isn't the problem. My SMTP DNS is perfectly configured in php.ini and a call to the 'mail()' function outside the PEAR::SOAP context works perfectly. Problems only seem to happen when I try to call 'mail()' from one of my wsdl server's methods. I already tried to use set_ini() inside the server's method to configure directly the smtp dns but it won't work either (does someone know why?). Thanks in advance for any help. Luis