I've recently installed RedHat 8 along with BIND and Postfix. The server and all applications are patched to the most recent versions. My Postfix server (runlevel6.com) can send mail just fine, but it can't receive mail. It can, however, send mail from itself to itself on the same machine.

Connecting remotely to the SMTP port on the mail server results in the following:
telnet runlevel6.com 25
220 ns1.runlevel6.com ESMTP Postfix
500 Error: bad syntax

Connecting via an email client either fails to send (with MS Outlook) or bounces with the following error:
"The following addresses had transient non-fatal errors..."

Nothing appears in the Postfix log when these connections are attempted.

Iptables is turned off on the mail server and the network firewall allows SMTP, IMAP, POP3, and DNS access.

My hosts.allow and hosts.deny have no entries.

lsof -i produces the following results:

[rootns1 sbin]# ./lsof -i
COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
portmap 491 rpc 3u IPv4 920 UDP *:sunrpc
portmap 491 rpc 4u IPv4 926 TCP *:sunrpc (LISTEN)
rpc.statd 510 rpcuser 4u IPv4 1002 UDP *:32768
rpc.statd 510 rpcuser 6u IPv4 1005 TCP *:32768 (LISTEN)
named 613 named 8u IPv4 1712 UDP *:32769
named 613 named 9u IPv4 1705 UDP ns1.runlevel6.com:domain
named 613 named 10u IPv4 1706 TCP ns1.runlevel6.com:domain (LISTEN)
named 613 named 11u IPv4 1710 UDP 192.168.0.202:domain
named 613 named 12u IPv4 1711 TCP 192.168.0.202:domain (LISTEN)
named 613 named 13u IPv4 1713 TCP ns1.runlevel6.com:rndc (LISTEN)
named 615 named 8u IPv4 1712 UDP *:32769
named 615 named 9u IPv4 1705 UDP ns1.runlevel6.com:domain
named 615 named 10u IPv4 1706 TCP ns1.runlevel6.com:domain (LISTEN)
named 615 named 11u IPv4 1710 UDP 192.168.0.202:domain
named 615 named 12u IPv4 1711 TCP 192.168.0.202:domain (LISTEN)
named 615 named 13u IPv4 1713 TCP ns1.runlevel6.com:rndc (LISTEN)
named 616 named 8u IPv4 1712 UDP *:32769
named 616 named 9u IPv4 1705 UDP ns1.runlevel6.com:domain
named 616 named 10u IPv4 1706 TCP ns1.runlevel6.com:domain (LISTEN)
named 616 named 11u IPv4 1710 UDP 192.168.0.202:domain
named 616 named 12u IPv4 1711 TCP 192.168.0.202:domain (LISTEN)
named 616 named 13u IPv4 1713 TCP ns1.runlevel6.com:rndc (LISTEN)
named 617 named 8u IPv4 1712 UDP *:32769
named 617 named 9u IPv4 1705 UDP ns1.runlevel6.com:domain
named 617 named 10u IPv4 1706 TCP ns1.runlevel6.com:domain (LISTEN)
named 617 named 11u IPv4 1710 UDP 192.168.0.202:domain
named 617 named 12u IPv4 1711 TCP 192.168.0.202:domain (LISTEN)
named 617 named 13u IPv4 1713 TCP ns1.runlevel6.com:rndc (LISTEN)
named 618 named 8u IPv4 1712 UDP *:32769
named 618 named 9u IPv4 1705 UDP ns1.runlevel6.com:domain
named 618 named 10u IPv4 1706 TCP ns1.runlevel6.com:domain (LISTEN)
named 618 named 11u IPv4 1710 UDP 192.168.0.202:domain
named 618 named 12u IPv4 1711 TCP 192.168.0.202:domain (LISTEN)
named 618 named 13u IPv4 1713 TCP ns1.runlevel6.com:rndc (LISTEN)
xinetd 632 root 5u IPv4 1721 TCP *:daytime (LISTEN)
xinetd 632 root 6u IPv4 1722 TCP *:imap (LISTEN)
xinetd 632 root 7u IPv4 1723 TCP *:imaps (LISTEN)
xinetd 632 root 9u IPv4 1724 TCP *pop3 (LISTEN)
xinetd 632 root 10u IPv4 1725 TCP *pop3s (LISTEN)
xinetd 632 root 11u IPv4 1726 TCP ns1.runlevel6.com:32769 (LISTEN)
xinetd 632 root 12u IPv4 1729 TCP *:telnet (LISTEN)
ntpd 646 ntp 4u IPv4 1769 UDP *:ntp
ntpd 646 ntp 5u IPv4 1770 UDP ns1.runlevel6.com:ntp
ntpd 646 ntp 6u IPv4 1771 UDP 192.168.0.202:ntp
lpd 660 lp 6u IPv4 1798 TCP *printer (LISTEN)
master 736 root 11u IPv4 1913 TCP *:smtp (LISTEN)
smbd 797 root 9u IPv4 2074 TCP *:netbios-ssn (LISTEN)
nmbd 801 root 6u IPv4 2077 UDP *:netbios-ns
nmbd 801 root 7u IPv4 2078 UDP *:netbios-dgm
nmbd 801 root 8u IPv4 2082 UDP 192.168.0.202:netbios-ns
nmbd 801 root 9u IPv4 2083 UDP 192.168.0.202:netbios-dgm
miniserv. 839 root 4u IPv4 2166 TCP *:10000 (LISTEN)
miniserv. 839 root 5u IPv4 2167 UDP *:10000
X 895 root 1u IPv4 2235 TCP *:x11 (LISTEN)

Any ideas or next step in troubleshooting would be greatly appreciated!

Thanks!

--gary
glraybariaur.com

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