...
Data Center (7.2.9 / 7.3.6 tested, probably earlier releases too) can cause concurrent retrieval and processing of emails from a common mailbox. Private support reference PS-14639, public issue tracker (not currently public). See related Atlassian JRA's below:
- https://jira.atlassian.com/browse/JRASERVER-65197 : JIRA Data Center Cache replication stops due to Heartbeat jobs failure
- https://jira.atlassian.com/browse/JRASERVER-65581 : JIRA creates duplicate issues when the standard mail handler has to process a large number of emails or large amounts of data.
...