When sending an email, an error was reported in the email tracking query: 550 "Sender" is invalid

Question

Use the Java code in Microsoft AP user: sendMail， An error occurred while sending. Before the error occurred, everything was normal when using this, but after a few days, the error appeared Another phenomenon is that this error only occurs when Azure invites users, but it does not occur when using administrator accounts.

Microsoft returned an error message to the email, and the following is the content of the response。

We haven't added or used this' qqqqq 'address, so we don't know why this email address appears