We have a message center use case to be implemented for Hybrid ACM Installation, I had a query whether we can use same sending email domains for Mid-sourcing and RT server. If not do we need to ramp up the sending domain used in RT server.
There is no need to do a IP warmup with Message Center as it's transactional message. The only limitation is the number of calls you can make to MC server as it's subject to limitation. You should contact your account manager to have the number of calls you subscribed to.
Also keep in mind you have a technical limitation of 300 TPS for Adobe Server per default.
Typically an IP warmup would involve the Adobe Campaign Deliverability team. To engage them, reach out to your Account Manager/CSM, Adobe Campaign Support if you don't already have a contact. If you do already have a Deliverability contact you can reach out to them directly to request the warmup.
Once engaged Adobe Deliverability can walk you through the warmup process.