About SyntaxError: Unexpected end of JSON input when sending zabbix test mail

On the zabbix web screen, when I tried to send a test email from the media type setting,
The following pop-up appears and cannot be sent:
SyntaxError: Unexpected end of JSON input

Do I need to set it up?

Currently, we have built it so that zabbix can monitor what's being monitored. I didn't build anything for mail, I just set up the snmp server on the zabbix screen.
Please let me know if there are any necessary settings for the Linux server.

Environment
·CentOS 8stream
·Zabbix 6.0