[CentOS] New mail server slow connecting to web server

Fri May 25 04:10:33 UTC 2018
Gary Stainburn <gary at ringways.co.uk>

Having successfully killed my (Centos 7) mail server I have had to build a new 

Thankfully I had a server build that I was about to start configuring as my 
new web server.

I appear to have set everything up okay, Exim, SpamAssassin, ClamAv, Dovecot, 
Postgresql, httpd etc.

Everything appears fine apart from when I try to connect to my web server.  
Whatever tried to connect suffers from a delay, and either times out or works 

I started off with problems connecting Exim to Postgresql on the web server. I 
then found that I couldn't connect using psql, or using Perl DBD-Pg.  I then 
found I couldn't SSH or SCP, dispite them both being on the same subnet.

The more I use the new system, better it appears to be, but the delay is still 

name resolution isn't the problem as I can nslookup both ways without 
problems, and specifying IP addresses makes no difference.  For testing I 
have disabled the firewall and selinux and that made no difference.

If I try to connect the other way there is no delay, but I cannot access the 
Postgresql server on my new mail server from the web server.

Anyone got any ideas?