I need help in emails

[evoltuionnet]

Im tryng to send emails to my customers, oscommerce sent it ok, but when they check their emails no emails receive from my store, then i try to submit enquiry from my store, it sends ok, but no enquiry receive in my inbox. third scenario, i tried to add new customer, i added ok, but no notifications that saying 'Thank you for ....' received by that new customer.

 

and the worst scenario an error appears during the purchasing process, im on the process of ordering and submiting payment method etc. and an error appear

 

the error says:

 

Fatal error: Cannot redeclare class smtp in C:\apache\htdocs\catalog\includes\classes\class.smtp.inc on line 12