I've a few coldfusion server running on our production. time to time mail connection verification failed randomly . the strange thing is that , while one server is failing to connect to SMTP server, the other servers are still connecting to the same SMTP server with the same SMTP server address and user credential . I don't do any changes on the failing server at all. we use AWS SES SMTP over TLS connection. when the server fail to connect to AWS SES over TLS , I change it to other SMTP server over standard 25 port with without TLS -- and it works fine.
the same server, I can send out email via windows command line using the same AWS SMTP with the same user credential no problem, but CF can't verified the connection so I am pretty sure this has something to do with CF.
I've gone through all of the logs and I couldn't find any useful error logs for this.