I'm afraid that Bamboo is not able to process the passwords stored in your mail server configuration and therefore you will need to recreate it.
There is a knowledge base article about this: After upgrading, Bamboo stop sending emails and throws 'Unknown encrypted data format' exception - Atlassian Documentation.
Please let me know if that fixes the issue.
I'm happy to announce that Bamboo 7.1 has been released and it’s overflowing with awesome new features. Top-voted issues First and foremost, a bunch of JAC top voted issues has been delivered - y...
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