I use mutt to send messages through exim4. Some messages lack a sender. Here is a log emtry showing that from: address is blank:
Apr 24 11:11:29 tev-mail-relay1 postfix/smtpd[510179]: connect from unknown[32.210.108.191] Apr 24 11:11:30 tev-mail-relay1 postfix/smtpd[510179]: Anonymous TLS connection established from unknown[32.210.108.191]: TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (2048 bits) server-digest SHA256 Apr 24 11:11:30 tev-mail-relay1 postfix/smtpd[510179]: NOQUEUE: milter-reject: MAIL from unknown[32.210.108.191]: 554 5.7.1 Empty Sender Address is prohibited through this server; from=<> proto=ESMTP helo=<lenin.histomat.net> sasl_username=<bro...@historicalmaterialism.info> Apr 24 11:11:30 tev-mail-relay1 postfix/smtpd[510179]: disconnect from unknown[32.210.108.191] ehlo=2 starttls=1 auth=1 mail=0/1 rcpt=0/1 bdat=0/1 quit=1 commands=5/8 521 5.5.1 Protocol error (154.24 ms) Unverified address I reconfigured exim4 and it has no problem.
