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Why this happens

A FolderClosedException (FCE) is caused when the connection between Jira and the inbound Mail server is closed abruptly by the mail server whilst mail is being retrieved. JEMH is not responsible for the mail connection, which This is caused by the configuration of your mail server, and the Jira environment.

Is this a JEMH bug?

No. The connection between Jira and the mail server is handled by Jira.

Symptoms

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Impact

As the FolderClosedException is triggered by the mail server whilst the mail is being retrieved, the mail in question is left in the mailbox, so no emails are lost. As the email could not be retrieved email processing will fail so JEMH will not create a comment/new issue.

Auditing

If using Inbound Auditing, an Audit event will be created however there will be no copy of the original email to be exported or used in a Support ZIP. Using auditing actions that rely on the email being present will result in a popup similar to the following:

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Links shown on the popup:

IMAP batch Sizes too low: https://thepluginpeople.atlassian.net/wiki/spaces/JEMH/pages/57606174/Download+performance+of+POP+vs+IMAP

Atlassian background info:
https://confluence.atlassian.com/jirakb/imap-mail-fails-with-folderclosedexception-in-logs-in-jira-server-385319403.html

Logs

A stack trace for the FolderClosedException will be added to the 'atlassian-jira-incoming-mail.log', such as the following example from the linked Atlassian documentation:

2013-07-12 09:52:50,478 ERROR [xxx] QuartzScheduler_Worker-3 ServiceRunner xxxx[xxxxx]: Exception: null
javax.mail.FolderClosedException
	at com.sun.mail.imap.IMAPMessage.getProtocol(IMAPMessage.java:145)
	at com.sun.mail.imap.IMAPMessage.getHeader(IMAPMessage.java:743)
	at com.atlassian.jira.service.services.mail.MailFetcherService$MessageProviderImpl.getAndProcessMail(MailFetcherService.java:257)
	at com.atlassian.jira.service.services.mail.MailFetcherService.runImpl(MailFetcherService.java:356)
	at com.atlassian.jira.service.services.file.AbstractMessageHandlingService.run(AbstractMessageHandlingService.java:257)
	at com.atlassian.jira.service.JiraServiceContainerImpl.run(JiraServiceContainerImpl.java:61)
	at com.atlassian.jira.service.ServiceRunner.execute(ServiceRunner.java:48)
	at org.quartz.core.JobRunShell.run(JobRunShell.java:195)

If enabled, JEMH Inbound Auditing will also add this exception to the Inbound processing report, and attempting to download the related email, or generate a Support ZIP the following popup will be shown:

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Causes

How to fix

Large Emails

Mail items that are too large and take an excessive time to be retrieved can result in a FolderClosedException, as the mail server interoperates the long retreival retrieval time as an error, and closes the connection. This can be compounded if using the IMAP protocol which has a low default ‘Fetch’ size which makes mail retrial of larger mail items significantly slower. See for more info and steps to increase IMAP ‘Fetch’ size:

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Mail servers have limits on the number of active connections for mail retrieval. If this limit is exceeded the mail server will close existing mail connections to create new connections. If mail is being retrieved and the connection is closed a FolderClosedException is created. Jira and JEMH work best when using a Mail server with limited mail connections, dedicated to automation.

If using multiple JEMH profiles to access the same mailbox, consider using a profile group to group multiple mail handlers to a single mail connection, to reduce traffic and boost performance:

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