New Mail Server Slow Connecting To Web Server

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

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 eventually.

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 there.

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?

One thought on - New Mail Server Slow Connecting To Web Server

  • Can you provide more detail here regarding what tests you performed? 
    Long delays are usually a timeout on a reverse DNS lookup (that is, a PTR lookup) on the connecting IP address.

    Connect to the server, and get the address that the server sees as its peer either from the log or using “ss -o state established -t”.  Use
    “time host $ip” to test the reverse lookup.  Send the output to the list.