Form submission does not send to shared mailbox

Hi there, my website is hosted at I have a contact form at the bottom of the page which is supposed to send an email to an Outlook shared mailbox However, no email is received from the form. If someone emails without using from the form I receive the email, so I know the mailbox is working. When I set the form to send to an individual user on our domain it works. The issue seems to be only with the form triggering an email to the shared mailbox. Can someone help?