I got your email enquiry yesterday but my reply was rejected at your incoming mail server as one of the email relays used seems to have been blocked due to abuse by your provider.
My response included the following questions:
1/ Do you get emails for comments or forgotten passwords from your site?
2/ Have you spoken to your hosting provider about this and their restrictions?
3/ Who is your hosting provider?
4/ Have you installed a mail logging plugin to check emails are generated in the first instance?
5/ Have you tried Configure SMTP plugin to channel the emails via an authenticated SMTP server to see if that helps?