I also doesn't find related article about this error message so far.
So, I want to confirm with you that if you resend 32 emails again, whether this phenomenon occurs? If you could send email successfully now, I guess this is may be a short-lived error, such as network fluctuations or something similar.
Here are sending limits for Exchange online, if email exceeds this limitation, we will get another error. There doesn't exist other limitation on the sending of emails. Since you could send a part of emails successfully, it means your configuration is correct.
If you want to deep in this phenomenon, you could contact the Office 365 teams and check whether they could find some information from the backend.
If the response is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.