I can't receive emails from this domain and several others. I have this error in the log, but I can't identify what it could be and how to fix it. These are the logs:

Jul 8 11:01:43 ksmg postfix/smtpd[31282]: connect from servermail.sudameris.com.py[190.128.229.115]
Jul 8 11:01:43 ksmg postfix/smtpd[31282]: setting up TLS connection from servermail.sudameris.com.py[190.128.229.115]
Jul 8 11:01:43 ksmg postfix/smtpd[31282]: Anonymous TLS connection established from servermail.sudameris.com.py[190.128.229.115]: TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)
Jul 8 11:01:43 ksmg postfix/smtpd[31282]: NOQUEUE: client=servermail.sudameris.com.py[190.128.229.115]
Jul 8 11:02:43 ksmg postfix/smtpd[31282]: timeout after DATA (0 bytes) from servermail.sudameris.com.py[190.128.229.115]
Jul 8 11:02:43 ksmg postfix/smtpd[31282]: disconnect from servermail.sudameris.com.py[190.128.229.115]
Jul 8 11:02:43 ksmg klms-smtp_proxy: Unexpected end of SMTP input: Bad file descriptor at void lms::filters::smtp_proxy::CopySmtpStream(std::istream&, std::ostream&, bool)

The sending server connects and negotiates TLS correctly, but the connection is dropped during the DATA phase. Postfix is not rejecting the mail. The error points to a local SMTP proxy/security filter (klms-smtp_proxy) interrupting the SMTP stream. Check, update, or temporarily disable that proxy and its SMTP inspection settings.