send bulk emails from SMTP exchange server to internal domain

Question

we are in Education environment that deals with more than 500,0000 students accounts, we plan to send notifications to a part of them (around 60,000 students) of their exam results.
we plan to do this by using on-prem Exchange (Version 15.1 (Build 2176.2)).
all emails will send to students internal domain e-mail. we will not send any e-mail to External domains.
we have office 365 hybrid setting configuration and all students mailboxes and sender email on office 365 cloud.
I put the sender email to the spam filter allowed list.
I'll use a PowerShell script to run this task.
is there any limitation on sending emails from on-prem exchange server? is there any concerns that i need to be awarded?

Answer 1

That will be throttled at that level. There is a high possibility it will get blocked as well.
I would recommend breaking it up and sending these out through out the day instead off all at once and watch for any rejections.

Please see the sending limits:

https://learn.microsoft.com/en-us/office365/servicedescriptions/exchange-online-service-description/exchange-online-limits#sending-limits

Answer 2

Thanks @Andy David - MVP
This means that if I need to send 60,000 email, I need minimum 6 users mailbox (send users) and keep the sending rate to max 30 email per minute.

right?