The problem may occur when you are using field Form will be sent from this Email in form configuration in website builder. For example, you use address in this field [email protected]. Then mails may not be received on your email account due to the fact that domain mysite.com does not have DNS record of type SPF (for more details, please see https://en.wikipedia.org/wiki/Sender_Policy_Framework). Due to this mails can be blocked by mail servers. If you are an owner of domain "mysite.com", you need to add SPF record in DNS configuration of your domain.

When you do not have field "Form will be sent from this Email" filled in, the address [email protected] is used (where "mysite.com" is replaced with your website domain name). In this case the reason of not receiving mails is the same as described above.