このエラーメッセージに関する原因と対処に関して説明します。
エラーメッセージ(英語)：
workmail mailbox unavailable
対処
関連リンク
AWS Developer Forums: Problems Receiving Mail w/ SES ...
https://forums.aws.amazon.com/thread.jspa?threadID=218014
Your domain's incoming mail is not ...
https://forums.aws.amazon.com/thread.jspa?threadID=222919
Can send email but i can't receive it ...
https://forums.aws.amazon.com/thread.jspa?threadID=216540
Amazon WorkMail account failing to receive email - Stack Overflow
https://stackoverflow.com/questions/47798822/amazon-workmail-account-failing-to-receive-email
AWS SES handle does't exist mailbox with lambda - Stack Overflow
https://stackoverflow.com/questions/37008354/aws-ses-handle-doest-exist-mailbox-with-lambda
amazon web services - AWS SES receive returns mailbox unavailable ...
https://serverfault.com/questions/890701/aws-ses-receive-returns-mailbox-unavailable
AWS Knowledge Center Videos: How do I set up WorkMail domain ...
https://www.youtube.com/watch?v=Ha-5K5cDY6E
https://www.youtube.com/watch?v=Ha-5K5cDY6E
?ドメインにメールを送信すると、"550 Requested action not taken: mailbox ...
https://support.plesk.com/hc/ja/articles/213947725--%E3%83%89%E3%83%A1%E3%82%A4%E3%83%B3%E3%81%AB%E3・・・
Hosted Exchange to Amazon WorkMail Migration Guide ? BitTitan ...
https://help.bittitan.com/hc/en-us/articles/115008265028-Hosted-Exchange-to-Amazon-WorkMail-Migratio・・・