Problems with sending a lot of Mails at the same Time

[DrDrThein]

Hello,
So I've been having trouble sending "big" amounts of mails at the same time with sendgrid. When sending 200 Mails or more, sendgrid will only send a certain amount and the rest stays pending for 1-2 hours and will only be received later.

I might need to send a several thousand emails at once at one point. I'm sending them with an email like, something@ourdomain.com

Our domain is authenticated and we have over 95% reputation.

I have to add that before when testing i had not added the something@ourdomain.com adress to the single sender Verification. Could that have been the only root of the problem, I didn't have time to retest since Iet that email adress be verified.

When sending the Emails, I add all the msg objects to an array and use the send function to send a single api call to the sendgrid api with all the msg objects ?

To add to this, we have the pro subscription with 100K included.

I feel like sending 200 mails shouldn't take more than 2 hours and I am doing something wrong