Exim connection attempts

Hestia Control Panel: v1.1.1
Operating System: Debian 10.4 (x86_64)

Checking the exim4 log at

cat /var/log/exim4/mainlog

It has been observed that it has multiple connections with attempted connection.
Is there any way to protect yourself?

In the firewall, pop and imap connections are not used for external connections, so they were limited to

Although smtp connections (25/465/587) are used to receive e-mails.

Any suggestion?