If your email stopped working out of nowhere, most likely, you have recently updated your domain's nameservers!
Domain nameservers determine where is your domain's DNS zone. For example, if you point your domain to Zyro via nameservers, your DNS zone is managed from Zyro. It means that all DNS records, including the ones responsible for email service, must be present in your domain's DNS zone (that's now managed from Zyro).
To access your domain's DNS zone at Zyro, go to the My domains page → click Manage domain → expand the DNS records section and add/delete particular DNS records.
Note: Most of the time, after updating nameservers, DNS records are fetched automatically, however, sometimes they must be recreated manually. If you're not sure what exactly records are responsible for your email service, you may contact your email hosting provider.