"Our workaround required us to install Microsoft SMTP server on the local IIS/ColdFusion webserver. We now use LOCALHOST when sending and then the local, always-on mail server forwards the message to our remote mail server. Since doing this, we haven't encountered any delivery issues." Well, that is discouraging. Every now and then (5 since 2018-01-01) we do get these errors so I would expect it to fail: "Error","scheduler-1","03/28/19","11:26:25",,"com.sun.mail.util.MailConnectException: Couldn't connect to host, port: smtp.our_domain_host.com, 25; timeout 120000; nested exception is: java.net.UnknownHostException: smtp.our_domain_host.com" There is also a tiny number of 451 errors. Anyway, thank you, Jamo, for the confirmation that this is a known issue.
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