ERROR: ORA-29278: SMTP transient error: 421 Service not available

Application that uses smtp to send emails, was working properly until we experienced a network outage, turns out someone at our network provider during a maintenance period cut one of the fiber cables. They repaired the cable and all our network processes came back, except the process that

is running on our oracle database server. I stopped and started the instance in question, but we're still getting the ora-29278 error.

The process works when we run from our backup database serve.

We stopped and started the sendmail process..