The error message NOQUEUE: reject: RCPT from ool-4355399b.dyn.optonline.net[67.85.57.155]: 454 4.7.1 : Relay access denied indicates Postfix is refusing to relay mail to external domains (yahoo.com in this case) from unauthorized clients.

Two primary configuration problems stand out:

mynetworks_style = host
relay_domains = proxy:mysql:/usr/local/etc/postfix/mysql_relay_domains_maps.cf list.ex-mailer.com

The mynetworks_style = host setting is too restrictive. Change to:

mynetworks = 127.0.0.0/8, 67.85.57.155/32
mynetworks_style = subnet

Or for testing purposes only:

mynetworks = 0.0.0.0/0

The MySQL-based relay configuration appears correct but needs verification. Test the query manually:

mysql -u doughnuts -p postfix -e "SELECT domain FROM domain WHERE domain='telecomm.com'"

Ensure the virtual mailbox domains are properly defined:

virtual_mailbox_domains = proxy:mysql:/usr/local/etc/postfix/mysql_virtual_domains_maps.cf

For authenticated relaying, verify your Dovecot SASL configuration:

# /usr/local/etc/dovecot/conf.d/10-master.conf
service auth {
  unix_listener /var/spool/postfix/private/auth {
    mode = 0660
    user = postfix
    group = postfix
  }
}

Use swaks for comprehensive SMTP testing:

swaks --to recipient@example.com --from user@telecomm.com --server localhost --port 587 --auth LOGIN --auth-user user@telecomm.com --auth-password 'password' --tls

1. Verify MySQL connection credentials in all .cf files
2. Check Postfix permissions: postfix check
3. Test DNS resolution for your domains
4. Review mail logs in real-time: tail -f /var/log/maillog

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The error NOQUEUE: reject: RCPT from ool-4355399b.dyn.optonline.net[67.85.57.155]: 454 4.7.1 : Relay access denied indicates Postfix is refusing to relay mail for external domains when the client isn't authenticated or listed in permitted networks.

Your current setup has several potential issues:

# Problematic configurations
mynetworks_style = host  # Too restrictive
relay_domains = proxy:mysql:/usr/local/etc/postfix/mysql_relay_domains_maps.cf list.ex-mailer.com
smtpd_recipient_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination

Here's how to properly configure relay permissions:

Option 1: Expand mynetworks

# /usr/local/etc/postfix/main.cf
mynetworks = 127.0.0.0/8, 67.85.57.155/32
mynetworks_style = subnet  # More flexible than 'host'

Option 2: Proper SASL Authentication

For authenticated relaying, ensure Dovecot SASL is properly configured:

# /usr/local/etc/postfix/main.cf
smtpd_sasl_type = dovecot
smtpd_sasl_path = private/auth
smtpd_sasl_auth_enable = yes
smtpd_sasl_security_options = noanonymous
broken_sasl_auth_clients = yes

Option 3: Relax Relay Restrictions

For testing purposes only, you could temporarily modify restrictions:

# Testing configuration (not recommended for production)
smtpd_recipient_restrictions = 
    permit_mynetworks,
    permit_sasl_authenticated,
    reject_unauth_pipelining,
    reject_invalid_hostname,
    warn_if_reject reject_unauth_destination,
    permit

Verify your MySQL relay domains configuration works correctly:

# Test MySQL query manually
mysql -u doughnuts -p postfix -e "SELECT domain FROM domain WHERE domain='telecomm.com' AND backupmx='0' AND active='1'"

Enable detailed logging to diagnose the exact rejection point:

# /usr/local/etc/postfix/main.cf
debug_peer_level = 2
debug_peer_list = 67.85.57.155
smtpd_verbose = yes

For a secure production setup, combine these elements:

# Secure production configuration
mynetworks = 127.0.0.0/8
smtpd_recipient_restrictions =
    permit_mynetworks,
    permit_sasl_authenticated,
    reject_non_fqdn_sender,
    reject_non_fqdn_recipient,
    reject_unauth_destination,
    reject_unauth_pipelining,
    reject_invalid_hostname,
    reject_rbl_client list.dsbl.org,
    reject_rbl_client bl.spamcop.net,
    reject_rbl_client sbl-xbl.spamhaus.org

Use these commands to verify your setup:

# Check Postfix configuration
postconf -n
postmap -q telecomm.com mysql:/usr/local/etc/postfix/mysql_relay_domains_maps.cf

# Test SMTP authentication
telnet localhost 25
EHLO example.com
MAIL FROM: <test@telecomm.com>
RCPT TO: <external@example.com>