There are a couple of issues here.

1. outlook does not use IMAP to talk to exchange which is what the mail server in O365 is. so what Outlook does and what any other mail client does can not be compared. Just as what I write probably would no make any sense literally translated into another language.

2. Microsoft has a somewhat quirky implementation of IMAP.

3. You XX'ed out the domain, so I must assume it is not a generic hotmail or outlook one. In this instance it is possible that the administrator has not enabled IMAP at all for the domain.

4. Do you use the exchange addon OWL https://addons.thunderbird.net/en-US/thunderbird/addon/owl-for-exchange/?src=ss This enable contacting o365 accounts without IMAP.

If I am getting it wrong here. It is possible that he issue may be localization of folder names. Is you Thunderbird version for the same language as the native server? Perhaps an English or a Chinese language version might not present the problem

Dear Matt,

Thank you. I use OWL as workaround though it's not free~

I also checked my email inbox, actually as your assumed, it is in Chinese.

This may caused the sync issue.

Thanks again.

Leo

The owl addon page has a support address, I suggest you use it. They are keep to fix issues especially bugs, and this sounds like a bug

I have an office 365 account setup in Thunderbird as well; what's interesting, Thunderbird can receive office 365 email but Thunderbird cannot send email using Office365 smtp settings; Because I used Thunderbird for multiple email accounts, I simply changed the outgoing server to another smtp account for outgoing mail and bypassed the proprietary bs that is Microsoft