dovecot rejecting connects

[Roy]

I am a newbie to dovecot but not postfix and centos

I created a new VM with Centos 8 and installed dovecot and postfix.  
Postfix is working fine but dovecot rejects connections from anything 
but the local machine.

Locally

   Trying 10.10.100.157...
   Connected to 10.10.100.157.
   Escape character is '^]'.
   * OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE 
IDLE STARTTLS AUTH=PLAIN] Dovecot ready.

Machine on same subnet.  Windows, Linux, etc.  Doesn't seem to matter

   telnet 10.10.100.157 143
   Connecting To 10.10.100.157...
   Could not open connection to the host, on port 143: Connect failed

I made sure the iptables are empty so it doesn't seem to be a firewall issue

I put some LOG statements in the iptables and it showed the connect 
packet arriving and the response packet was ICMP type 3 code 13.

Any ideas?

Roy