I've been using Zoho Mail for many years to access my email accounts.

But suddenly, Zoho is no longer able to access my emails from my Ionos servers. The accounts show an authentication failure error. And if I try and edit the email account, or click the account checkbox to enabled it, I get a toast message that says unknown command.

I have contacted Ionos and was told they've changed nothing on their end. Also, I grabbed an email client program and entered the same credentials, and it was able to retrieve email from these servers with no issues.