I have two servers, each server running a different 1.5 forum. Both of these forums are configured to use a SMTP server for email sending. This SMTP server is a VPS that I also own. On both forums at Email Options I have:
The SMTP server is running Postfix and is protected against unauthorized use by iptables and the mynetworks directive in the Postfix config file.
Well the problem is that one of my forums is randomly and many times a day logging the following errors:
Email to xxxxxxxx failed: Connection refused Email to xxxxxxxx failed: Could not open socket Email to xxxxxxxx failed: No connection has been established to smtp.mydomain.com
I know that in 1.5 the email is now being sent in a deferred process (which implies a batch of emails to be sent at once unless I'm wrong). I have to say however that this problem has been present even in previous versions like 1.4 and even 1.3 IIRC.