When transferring a domain, mail through phpMailer does not work?

Question

PHPMailer

Good afternoon, please tell me, I made a website for the customer, set up a feedback form on my domain from yandex mail (not from the hosting mail) via phpMailer to the customer's mail. Everything worked fine, because there was a notification that a letter from the site had been sent. Now transferred to the customer's domain, however, it is apparently still a test one, because it looks like a second-level domain, like company.1gb.ru. and their email is not working. Tell me, do I need to contact their hosting and find out everything there? Sorry for the question, the first customer is simple.

Answer 1

Hello. Can I see the code of the email sending settings file?