Hi Susan71, if this is still happening to you.Are you using a mail client and if so which or is this affecting webmail? Please update your community profile to include your full name, landline and mobile number, so that I can pass your details over to the Networks team.
To add your details you click on MY SETTINGS above the thread in blue then choose PERSONAL INFORMATION after adding your details add the email address/es in the private section and click save changes at the bottom of the page.
I'll also need you to add one or more of the mail addresses that have failed to receive the mail. Ideally along with the time and date sent.