If you notice that emails from your newly connected Office inbox are bouncing due to 550 5.7.708 Service unavailable. Access denied, traffic not accepted from this IP, this article will help you to fix it.
This is a common problem when you have an Office 365 trial with an Exchange Online license.
To fix this issue, please use the Office 365 delist portal to remove yourself from the blocked senders list. You can see the instructions in this article:
https://learn.microsoft.com/sk-sk/defender-office-365/external-senders-use-the-delist-portal-to-unblock-yourself?redirectedfrom=MSDN
Alternatively, you can contact Microsoft support and ask them to whitelist your IP.
Once they do that, this issue stops.
Until then I recommend pausing the warmup for this inbox so your reputation doesn't suffer.