Customers not able to enter account or reset password

HI ! I have noticed that for some time now, I have little recurring customers and I have had 2 customers recently that say that they cannot connect into their account or even able to reset the password. I think don’t even receive the email for the reset password. I just don’t know what is going on or what to do. Is it Shopify or can it the GoDaddy email account that is the problem ? Does resetting the password email use Shopify’s server’s only, or does it use my email service provider ?

Did anyone have this problem ? What do I do ? Thanks !