Do I need my own IP address?

In our experience, having your own IP address only makes sense if you send more than 100,000 emails per month.

When we assign an IP address, we warm it up in advance by sending emails in ever larger "packages". A few hundred at the beginning to several hundred thousand emails at the end. 

If you then send fewer emails via the IP address, the IP address cools down again and the delivery rate decreases.