Activation and Confirmation Emails not received

Hi,

I’m using the User Verification plugin in conjunction with MemberPress.

I did have it working where people that signed up to the free membership received a confirmation email to verify their account.

For some reason now when people sign up they don’t receive the confirmation email? This is happening on most of the signups, it seems that some domains are not receiving the emails.

Would it be possible to have a look and advise.

Many thanks,
Mazen