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A Forward Notification is an email notification sent by JEMH to Profile > Notification > Forward Users to notify about mail that is not processed successfully and that something went wrong or is wrong with the configuration. Sometimes recovery action is required, sometimes not, but indicates other problems that you as a Jira admin should be aware of.
Forward users/email addresses must not be the same as a Catchemail (mailbox address) as this causes a mail loop. Detection is automatic from JEMH V4.2.11, edit time feedback is given in this case:
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Why did I get a Forward notification from JEMH
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