I have my site hosting with InfinityFree, but my domain with IONOS. I have just realised that my email I have with IONOS doesn’t work. It has MX issues.
I was advised by IONOS Support that:
“To resolve this issue, you need to contact your nameserver provider and ask them to add the MX records for IONOS. The MX records can only be added through their system, as they are managing your domain’s DNS.”