Automatic Emails in PHP

[mateobus]

Hello all. I have recently switched from a dedicated plan to a shared hosting plan. Many of my old scripts (including open source scripts) use php to send an automatic email to people in order to register for different sections (much like this forum). Many of my users have complained that they havent recieved the confirmation email. It seems like these php functions are no longer working. Is there something that I need to do through plesk to allow this? Any help is appreciated. Thanks.