I had some errors while sending a email to my postfix linux server: Helo command rejected Host not found
<server.mydomain.lan>: Helo command rejected: Host not found; from=<fail2ban@server.mydomain.lan>
The problem is that lan and local Domains don’t have a correct HELO command.
Solution
Permit sasl authenticated users. When you are logged in with the correct credentials then the helo check doesn’t execute and you can send the mails with your local fqdn. This line should be inserted right at the beginning! If you don’t do this it won’t work because these rules match from the top to the bottom.
smtpd_helo_restrictions =
permit_mynetworks,
#alle authentifizierten benutzer erlauben – permit lan und local domains
permit_sasl_authenticated,
reject_invalid_hostname,
reject_unknown_hostname,
reject_non_fqdn_helo_hostname,
reject_unknown_helo_hostname,
reject_unauth_pipelining,
reject_unknown_client_hostname
