How to find which outgoing emails were blocked ?

How to find which outgoing emails were blocked ?

Hi,

One of our Zoho emailids was blocked temporarily in the afternoon when we were automatically sending new updates in email to our users using our server and using SMTP.

We know several outgoing emails were blocked and they didn't go out to our users.

Now we want to find out which outgoing emails were blocked or rejected by Zoho ? So that for those emailids, we can retrigger emails.

regards
Nidhi