Services Freeze after Network Interruption
After a temporary outage of the network or the DNS server, JIRA's services stop working.
Typically, the first service outage noticed is Email, and there will be no processing of inbound nor sending of outbound messages. An absence of log messages from the QuartzWorker service is also a cue.
This is caused from faulty timeout recovery from a failed DNS lookup.
At this time, the only known solution is to restart JIRA. As this is caused by external factors, it is important to ensure the reliability of the network services that are required by JIRA.