Why can't I enter @ (or blank) as name in the MX record?

[sp007c]

I am trying to setup a Third-Party mail service using these instructions:

E-Mail-Zustellung konfigurieren – Zoho Mail einrichten

Anweisungen zum Konfigurieren der E-Mail-Zustellung und zum Aktualisieren von MX-Einträgen für spezifische DNS-Provider.

www.zoho.com

However, my DirectAdmin complains that "@" is an "Invalid DNS Name":



What am I supposed to do instead?

 

[Zhenyapan]

@ = domain.name
so just put full domain name there with the dot at the end.