[Socket Error # 11001 Host not found.]

I'm trying to make a prestashop module that auto-send a E-mail to customer. I'm runnnig this php class:

When I do so i get the error: Socket Error # 11001 Host not found. The smtp_port is set on 25.

I need your help!

[Database select statement]

The thing that i need is the, Firstname, Lastname and Email of the customer who purchased the product with reference 1800 and 1898. before 2018-05-18.

I have tried this query:

select pscustomer.firstname, lastname , email from pscustomer inner join psproduct where psproduct.reference in (1800,1898) and psproduct.dateadd >= 2018-05-18

but that gives just all the information of ALL customers back and that's not what i want.

Pleasse help my!