When JIRA is configured to parse incoming mails (from POP/IMAP) to create new issues, it will go into a loop repeatedly creating issues if the email attachment cannot be parsed.

For instance, if an email's attachment has an encoding Java doesn't support (eg. utf-7 - see JRA-5812), then JIRA loops, creating an issue and then failing to clear it because the attachment isn't processed.

2007-01-31 12:49:34,206 JiraQuartzScheduler_Worker-0 WARN [jira.issue.managers.DefaultAttachmentManager] Cannot create attachment without a filename - inline content? See http://jira.atlassian.com/browse/JRA-10825 (file=tempattach30736dat).
2007-01-31 12:49:34,208 JiraQuartzScheduler_Worker-0 ERROR [service.util.handler.CreateIssueHandler] Could not create issue!
java.io.UnsupportedEncodingException: unicode-1-1-utf-7
at sun.nio.cs.StreamDecoder.forInputStreamReader(StreamDecoder.java:52)
at java.io.InputStreamReader.<init>(InputStreamReader.java:83)
at com.sun.mail.handlers.text_plain.getContent(text_plain.java:64)
at javax.activation.DataSourceDataContentHandler.getContent(DataHandler.java:774)
at javax.activation.DataHandler.getContent(DataHandler.java:521)
at javax.mail.internet.MimeBodyPart.getContent(MimeBodyPart.java:603)
at com.atlassian.jira.service.util.handler.AbstractMessageHandler.handleMultipart(AbstractMessageHandler.java:236)
at com.atlassian.jira.service.util.handler.AbstractMessageHandler.createAttachmentsForMessage(AbstractMessageHandler.java:201)
at com.atlassian.jira.service.util.handler.CreateIssueHandler.handleMessage(CreateIssueHandler.java:201)
at com.atlassian.jira.service.util.handler.CreateOrCommentHandler.handleMessage(CreateOrCommentHandler.java:115)
at com.atlassian.jira.service.services.mail.MailFetcherService.run(MailFetcherService.java:190)
at com.atlassian.jira.service.JiraServiceContainerImpl.run(JiraServiceContainerImpl.java:67)
at com.atlassian.jira.service.ServiceRunner.execute(ServiceRunner.java:48)
at org.quartz.core.JobRunShell.run(JobRunShell.java:191)
at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:516)
2007-01-31 12:51:34,224 JiraQuartzScheduler_Worker-3 WARN [jira.issue.managers.DefaultAttachmentManager] Cannot create attachment without a filename - inline content? See http://jira.atlassian.com/browse/JRA-10825 (file=tempattach30737dat).
2007-01-31 12:51:34,226 JiraQuartzScheduler_Worker-3 ERROR [service.util.handler.CreateIssueHandler] Could not create issue!
java.io.UnsupportedEncodingException: unicode-1-1-utf-7
at sun.nio.cs.StreamDecoder.forInputStreamReader(StreamDecoder.java:52)
at java.io.InputStreamReader.<init>(InputStreamReader.java:83)
at com.sun.mail.handlers.text_plain.getContent(text_plain.java:64)
at javax.activation.DataSourceDataContentHandler.getContent(DataHandler.java:774)
at javax.activation.DataHandler.getContent(DataHandler.java:521)
at javax.mail.internet.MimeBodyPart.getContent(MimeBodyPart.java:603)
at com.atlassian.jira.service.util.handler.AbstractMessageHandler.handleMultipart(AbstractMessageHandler.java:236)
at com.atlassian.jira.service.util.handler.AbstractMessageHandler.createAttachmentsForMessage(AbstractMessageHandler.java:201)
at com.atlassian.jira.service.util.handler.CreateIssueHandler.handleMessage(CreateIssueHandler.java:201)
at com.atlassian.jira.service.util.handler.CreateOrCommentHandler.handleMessage(CreateOrCommentHandler.java:115)
at com.atlassian.jira.service.services.mail.MailFetcherService.run(MailFetcherService.java:190)
at com.atlassian.jira.service.JiraServiceContainerImpl.run(JiraServiceContainerImpl.java:67)
at com.atlassian.jira.service.ServiceRunner.execute(ServiceRunner.java:48)
at org.quartz.core.JobRunShell.run(JobRunShell.java:191)