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JEMHC can’t use the built-in mailbox address provided by Atlassian, so you must use an external one. When doing so you may need allow connections from the JEMHC public IP address to to your mail service. For finer grained access control, you could setup dedicated certificates that only your configuration has.
Allowlisting IP addressed used by JEMHC
Your mailhost may require JEMHC public IP addresses to be allowed. Your mailhost may have to be configured to be allowed to relay mail sending (symptoms of this are mail that doesn't deliver outside your domain).
EU and DE app data location IP addresses to allow
What's different?
Data Storage
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