After many years working with Virtualmin systems I have to admit defeat by Postfix ! This is a VPS hosting my personal domain (real name replaced with <…> in the config posted below). Fresh Ubuntu Linux 24.04.3 installation running Virtualmin 7.50.2 GPL.
Receiving email works fine and sending from Webmin and Usermin also works. But whichever device I try to send an email from to an external domain I get “relay access denied” or “Resending limits exceeded”. Devices tried: Thunderbird on PC and K9 Mail on Android Phone.
I even went that far to setup an SSH mailtunnel on the PC, but still localhost also gets denied.
I have activated the following things in Virtualmin: Milter, Spamassassin, Greylisting, Fail2ban and FirewallD, all up and running. My IP’s I am connecting from are not in the Fail2ban jail.
Does anyone have a clue what could be wrong in my Postfix config?
Postfix Version: 3.8.6
Hostname nl.<myhost.name>
System Linux nl.<myhost.name> 6.8.0-88-generic #89-Ubuntu SMP PREEMPT_DYNAMIC Sat Oct 11 01:02:46 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux
Mailbox locking methods
flock
fcntl
dotlock
Supported Lookup Tables
btree
cidr
environ
fail
hash
inline
internal
memcache
nis
pcre
pipemap
proxy
randmap
regexp
socketmap
static
tcp
texthash
unionmap
unix
main.cf
non-default parameters
alias_maps hash:/etc/aliases
allow_percent_hack no
append_dot_mydomain no
biff no
broken_sasl_auth_clients yes
compatibility_level 3.6
disable_vrfy_command yes
home_mailbox Maildir/
inet_protocols ipv4
mailbox_command /usr/bin/procmail-wrapper -o -a $DOMAIN -d $LOGNAME
mailbox_size_limit 0
milter_default_action accept
mydestination $myhostname, mail.<myhost.name>, nl.<myhost.name>, localhost.<myhost.name>, localhost
mynetworks 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
myorigin mail.<myhost.name>
non_smtpd_milters local:/var/run/milter-greylist/milter-greylist.sock,inet:127.0.0.1:8891
readme_directory no
recipient_delimiter +
resolve_dequoted_address no
sender_bcc_maps hash:/etc/postfix/bcc
sender_dependent_default_transport_maps hash:/etc/postfix/dependent
smtp_dns_support_level dnssec
smtp_tls_CApath /etc/ssl/certs
smtp_tls_security_level dane
smtp_tls_session_cache_database btree:${data_directory}/smtp_scache
smtpd_banner mail.<myhost.name>
smtpd_client_restrictions permit_mynetworks check_client_access hash:/etc/postfix/sender_access reject_rbl_client zen.spamhaus.org reject_rhsbl_client dbl.spamhaus.org permit_sasl_authenticated reject_unknown_reverse_client_hostname
smtpd_helo_required yes
smtpd_milters local:/var/run/milter-greylist/milter-greylist.sock,inet:127.0.0.1:8891
smtpd_recipient_restrictions permit_mynetworks permit_sasl_authenticated reject_unknown_reverse_client_hostname reject_unauth_destination
smtpd_relay_restrictions defer_unauth_destination permit_mynetworks permit_sasl_authenticated reject_unknown_reverse_client_hostname
smtpd_sasl_auth_enable yes
smtpd_tls_CAfile /etc/postfix/postfix.ca.pem
smtpd_tls_cert_file /etc/postfix/postfix.cert.pem
smtpd_tls_key_file /etc/postfix/postfix.key.pem
smtpd_tls_mandatory_protocols !SSLv2, !SSLv3, !TLSv1, !TLSv1.1
smtpd_tls_security_level may
tls_server_sni_maps hash:/etc/postfix/sni_map
virtual_alias_maps hash:/etc/postfix/virtual
main.cf
parameters defined as per defaults
alias_database hash:/etc/aliases
smtp_host_lookup dns
