need fully-qualified hostname with smtp-auth port 25

Hello dear community,

I have the following problem:
Due to the requirements of some old systems in my network, I have set up authentication via SMTP on port 25.

/root/mailcow-dockerized/data/conf/postfix/main.cf
smtpd_tls_auth_only = no

/root/mailcow-dockerized/data/conf/postfix/master.cf
smtpd_sasl_auth_enable=yes

Unfortunately, I receive the following error message when authenticating via port 25:
NOQUEUE: reject: RCPT from unknown[IP-ADRESS]: 504 5.5.2 <SRV-MS01>: Helo command rejected: need fully-qualified hostname; from=mail@internaldomain.de to=mail@externaldomain.de proto=ESMTP helo=<SRV-MS01>

If I connect via TLS/SSL, the problem does not occur!

I then added the following lines to main.cf:

smtpd_helo_restrictions =
permit_mynetworks,
permit_sasl_authenticated,
reject_invalid_helo_hostname,
reject_non_fqdn_helo_hostname,
permit

I have also adjusted the following setting:
smtpd_helo_required = no

I then restarted all services and the system, but I get the same error: need fully-qualified hostname
What do I have to do so that I do not need a fully-qualified hostname via port 25?